media: atomisp: ov2680: don't declare unused vars

drivers/staging/media/atomisp/i2c/atomisp-ov2680.c: In function ‘__ov2680_set_exposure’:
drivers/staging/media/atomisp/i2c/atomisp-ov2680.c:400:10: warning: variable ‘hts’ set but not used [-Wunused-but-set-variable]
  u16 vts,hts;
          ^~~
drivers/staging/media/atomisp/i2c/atomisp-ov2680.c: In function ‘ov2680_detect’:
drivers/staging/media/atomisp/i2c/atomisp-ov2680.c:1164:5: warning: variable ‘revision’ set but not used [-Wunused-but-set-variable]
  u8 revision;
     ^~~~~~~~

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