media: coda: cast an operand of multiplication to a larger type

If the width and height are 0xffff (or close), the result of a
multiplication will overflow.
Cast to a larger type to avoid undefined behavior.

Such values are possible in CODA7, but unlikely.

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Fixes: 918c66fd ("[media] coda: add CODA7541 decoding support")
Signed-off-by: Anastasia Belova <abelova@astralinux.ru>
Signed-off-by: Sebastian Fricke <sebastian.fricke@collabora.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>