If dobj->control is not initialized we end up in an OOPs during
skl_tplg_complete:

[   26.553358] BUG: kernel NULL pointer dereference, address:
0000000000000078
[   26.561151] #PF: supervisor read access in kernel mode
[   26.566897] #PF: error_code(0x0000) - not-present page
[   26.572642] PGD 0 P4D 0
[   26.575479] Oops: 0000 [#1] PREEMPT SMP PTI
[   26.580158] CPU: 2 PID: 2082 Comm: udevd Tainted: G         C
5.4.81 #4
[   26.588232] Hardware name: HP Soraka/Soraka, BIOS
Google_Soraka.10431.106.0 12/03/2019
[   26.597082] RIP: 0010:skl_tplg_complete+0x70/0x144 [snd_soc_skl]

Fixes: 2d744ecf ("ASoC: Intel: Skylake: Automatic DMIC format configuration according to information from NHL")
Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
Reviewed-by: Cezary Rojewski <cezary.rojewski@intel.com>
Tested-by: Lukasz Majczak <lma@semihalf.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20210121171644.131059-1-ribalda@chromium.orgSigned-off-by: Mark Brown <broonie@kernel.org>