[media] atomisp: Make undeclared symbols static

Fix sparse warnings: "symbol not declared; should it be static?"

Signed-off-by: Guru Das Srinagesh <gurooodas@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>