media: staging: media: atomisp: fix CamelCase variable naming

Mixed case variable names are discouraged and they result in checkpatch
script "Avoid CamelCase" warnings. Replace such CamelCase variable names
by lower case strings according to the coding style guidelines.

Signed-off-by: Deepak R Varma <drv@mailo.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Acked-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>