media: coda: ctx->codec is not NULL in coda_alloc_framebuffers

This fixes a smatch warning:

    drivers/media/platform/coda/coda-bit.c:415 coda_alloc_framebuffers()
    error: we previously assumed 'ctx->codec' could be null (see line 396)

coda_alloc_framebuffers() is called from coda_start_encoding() and
__coda_start_decoding(). Both dereference ctx->codec before calling
coda_alloc_framebuffers() in lines 935 and 1649, so ctx->codec can not
be NULL.

Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
Signed-off-by: Hans Verkuil <hansverk@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>