The function hlwd_pic_init can be made static, so do it. Fix the following
warning treated as error (W=1):

../arch/powerpc/platforms/embedded6xx/hlwd-pic.c:158:20: error: no previous prototype for ‘hlwd_pic_init’ [-Werror=missing-prototypes]
Signed-off-by: Mathieu Malaterre <malat@debian.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>