media: smiapp: Remove quirk function for writing a single 8-bit register

This function is no longer needed as the smiapp_write() function can be
used to write 8-bit registers with plain register addresses.

Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>