Take the regulator lock before applying system load.

Fixes the following lockdep splat:

[    5.583581] WARNING: CPU: 1 PID: 16 at drivers/regulator/core.c:925 drms_uA_update+0x114/0x360
[    5.588467] Modules linked in:
[    5.596833] CPU: 1 PID: 16 Comm: kworker/1:0 Not tainted 5.0.0-rc6-next-20190213-00002-g0fce66ab480f #18
[    5.599933] Hardware name: Qualcomm Technologies, Inc. APQ 8016 SBC (DT)
[    5.609544] Workqueue: events qcom_channel_state_worker
[    5.616209] pstate: 60000005 (nZCv daif -PAN -UAO)
[    5.621152] pc : drms_uA_update+0x114/0x360
[    5.626006] lr : drms_uA_update+0x110/0x360
[    5.630084] sp : ffff0000124b3490
[    5.634242] x29: ffff0000124b3490 x28: ffff800005326e00
[    5.637735] x27: ffff0000124b35f8 x26: 000000000032bc48
[    5.643117] x25: ffff800004c7e800 x24: ffff800004c6d500
[    5.648411] x23: ffff800004c38a80 x22: 00000000000000d1
[    5.653706] x21: 00000000001ab3f0 x20: ffff800004c7e800
[    5.659001] x19: ffff0000114c3000 x18: ffffffffffffffff
[    5.664297] x17: 0000000000000000 x16: 0000000000000000
[    5.669592] x15: ffff0000114c3808 x14: 0720072007200720
[    5.674888] x13: 00000000199c9b28 x12: ffff80002bcccc40
[    5.680183] x11: ffff000012286000 x10: ffff0000114c3808
[    5.685477] x9 : 0720072007200720 x8 : ffff000010e9e808
[    5.690772] x7 : ffff0000106da568 x6 : 0000000000000000
[    5.696067] x5 : 0000000000000000 x4 : 0000000000000000
[    5.701362] x3 : 0000000000000004 x2 : 0000000000000000
[    5.706658] x1 : 0000000000000000 x0 : 0000000000000000
[    5.711952] Call trace:
[    5.717223]  drms_uA_update+0x114/0x360
[    5.719405]  regulator_register+0xb30/0x1140
[    5.723230]  devm_regulator_register+0x4c/0xa8
[    5.727745]  rpm_reg_probe+0xfc/0x1b0
[    5.731992]  platform_drv_probe+0x50/0xa0
[    5.735727]  really_probe+0x20c/0x2b8
[    5.739718]  driver_probe_device+0x58/0x100
[    5.743368]  __device_attach_driver+0x90/0xd0
[    5.747363]  bus_for_each_drv+0x64/0xc8
[    5.751870]  __device_attach+0xd8/0x138
[    5.755516]  device_initial_probe+0x10/0x18
[    5.759341]  bus_probe_device+0x98/0xa0
[    5.763502]  device_add+0x3d0/0x640
[    5.767319]  of_device_add+0x48/0x58
[    5.770793]  of_platform_device_create_pdata+0xb0/0x128
[    5.774629]  of_platform_bus_create+0x174/0x370
[    5.779569]  of_platform_populate+0x78/0xe0
[    5.784082]  qcom_smd_rpm_probe+0x80/0xa0
[    5.788245]  rpmsg_dev_probe+0x114/0x1a0
[    5.792411]  really_probe+0x20c/0x2b8
[    5.796401]  driver_probe_device+0x58/0x100
[    5.799964]  __device_attach_driver+0x90/0xd0
[    5.803960]  bus_for_each_drv+0x64/0xc8
[    5.808468]  __device_attach+0xd8/0x138
[    5.812115]  device_initial_probe+0x10/0x18
[    5.815936]  bus_probe_device+0x98/0xa0
[    5.820099]  device_add+0x3d0/0x640
[    5.823916]  device_register+0x1c/0x28
[    5.827391]  rpmsg_register_device+0x4c/0x90
[    5.831216]  qcom_channel_state_worker+0x170/0x298
[    5.835651]  process_one_work+0x294/0x6e8
[    5.840241]  worker_thread+0x40/0x450
[    5.844318]  kthread+0x11c/0x120
[    5.847961]  ret_from_fork+0x10/0x18
[    5.851260] irq event stamp: 9090
[    5.854820] hardirqs last  enabled at (9089): [<ffff000010160798>] console_unlock+0x3e0/0x5b0
[    5.858086] hardirqs last disabled at (9090): [<ffff0000100817cc>] do_debug_exception+0x104/0x140
[    5.866596] softirqs last  enabled at (9086): [<ffff000010082024>] __do_softirq+0x474/0x574
[    5.875446] softirqs last disabled at (9079): [<ffff0000100f2254>] irq_exit+0x13c/0x148
[    5.883598] ---[ end trace 6984ef7f081afa21 ]---

Fixes: fa94e48e ("regulator: core: Apply system load even if no consumer loads")
Signed-off-by: Niklas Cassel <niklas.cassel@linaro.org>
Signed-off-by: Mark Brown <broonie@kernel.org>