V4L/DVB: gspca cpia1: make local functions static

Make the local functions static. Note that the function command_setlights() is
currently not called from anywhere.

This will remove the following sparse warnings (see "make C=1"):
 * symbol 'command_setformat' was not declared. Should it be static?
 * symbol 'command_setcolourparams' was not declared. Should it be static?
 * symbol 'command_setapcor' was not declared. Should it be static?
 * symbol 'command_setvloffset' was not declared. Should it be static?
 * symbol 'command_setexposure' was not declared. Should it be static?
 * symbol 'command_setcolourbalance' was not declared. Should it be static?
 * symbol 'command_setcompressiontarget' was not declared. Should it be static?
 * symbol 'command_setyuvtresh' was not declared. Should it be static?
 * symbol 'command_setcompressionparams' was not declared. Should it be static?
 * symbol 'command_setcompression' was not declared. Should it be static?
 * symbol 'command_setsensorfps' was not declared. Should it be static?
 * symbol 'command_setflickerctrl' was not declared. Should it be static?
 * symbol 'command_setecptiming' was not declared. Should it be static?
 * symbol 'command_pause' was not declared. Should it be static?
 * symbol 'command_resume' was not declared. Should it be static?
 * symbol 'command_setlights' was not declared. Should it be static?

Signed-off-by: Márton Németh <nm127@freemail.hu>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>