[media] s5c73m3: Staticize some symbols

Fixes the following sparse warnings:
drivers/media/i2c/s5c73m3/s5c73m3-core.c:42:5: warning:
symbol 'boot_from_rom' was not declared. Should it be static?
drivers/media/i2c/s5c73m3/s5c73m3-core.c:45:5: warning:
symbol 'update_fw' was not declared. Should it be static?
drivers/media/i2c/s5c73m3/s5c73m3-core.c:298:5: warning:
symbol 's5c73m3_isp_comm_result' was not declared. Should it be static?

Signed-off-by: Sachin Kamat <sachin.kamat@linaro.org>
Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>