Add simple 'functionality' member to dummy Exynos IS i2c adapter to make
i2c core happy and get rid of NULL pointer dereference during Exynos4 IS
probe since v4.10-rc1:

Unable to handle kernel NULL pointer dereference at virtual address 00000000
pgd = c0004000
[00000000] *pgd=00000000
Internal error: Oops: 80000005 [#1] PREEMPT SMP ARM
Modules linked in:
CPU: 1 PID: 100 Comm: kworker/1:2 Not tainted 4.10.0-rc6-next-20170131-00054-g39e6e4233de6 #1921
Hardware name: SAMSUNG EXYNOS (Flattened Device Tree)
Workqueue: events deferred_probe_work_func
task: ef2e0000 task.stack: ef2ec000
PC is at 0x0
LR is at i2c_register_adapter+0x98/0x5cc
...
[<c05040bc>] (i2c_register_adapter) from [<c05379d4>] (fimc_is_i2c_probe+0x84/0xe4)
[<c05379d4>] (fimc_is_i2c_probe) from [<c041b5c8>] (platform_drv_probe+0x50/0xb0)
[<c041b5c8>] (platform_drv_probe) from [<c0419f48>] (driver_probe_device+0x234/0x2dc)
[<c0419f48>] (driver_probe_device) from [<c04184e0>] (bus_for_each_drv+0x44/0x8c)
[<c04184e0>] (bus_for_each_drv) from [<c0419c8c>] (__device_attach+0x9c/0x100)
[<c0419c8c>] (__device_attach) from [<c0419374>] (bus_probe_device+0x84/0x8c)
[<c0419374>] (bus_probe_device) from [<c04178d4>] (device_add+0x380/0x528)
[<c04178d4>] (device_add) from [<c05aceb4>] (of_platform_device_create_pdata+0x70/0xa4)
[<c05aceb4>] (of_platform_device_create_pdata) from [<c05acfd4>] (of_platform_bus_create+0xec/0x320)
[<c05acfd4>] (of_platform_bus_create) from [<c05ad264>] (of_platform_populate+0x5c/0xac)
[<c05ad264>] (of_platform_populate) from [<c0533420>] (fimc_is_probe+0x1c0/0x4cc)
[<c0533420>] (fimc_is_probe) from [<c041b5c8>] (platform_drv_probe+0x50/0xb0)
[<c041b5c8>] (platform_drv_probe) from [<c0419f48>] (driver_probe_device+0x234/0x2dc)
[<c0419f48>] (driver_probe_device) from [<c04184e0>] (bus_for_each_drv+0x44/0x8c)
[<c04184e0>] (bus_for_each_drv) from [<c0419c8c>] (__device_attach+0x9c/0x100)
[<c0419c8c>] (__device_attach) from [<c0419374>] (bus_probe_device+0x84/0x8c)
[<c0419374>] (bus_probe_device) from [<c04197a8>] (deferred_probe_work_func+0x60/0x8c)
[<c04197a8>] (deferred_probe_work_func) from [<c01329a4>] (process_one_work+0x120/0x31c)
[<c01329a4>] (process_one_work) from [<c0132bc8>] (process_scheduled_works+0x28/0x38)
[<c0132bc8>] (process_scheduled_works) from [<c0132ddc>] (worker_thread+0x204/0x4ac)
[<c0132ddc>] (worker_thread) from [<c01381b8>] (kthread+0xfc/0x134)
[<c01381b8>] (kthread) from [<c01078b8>] (ret_from_fork+0x14/0x3c)
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>