media: siano: fix a potential integer overflow

Add suffix ULL to constant 65535 in order to avoid a potential
integer overflow. This constant is used in a context that
expects an expression of type u64.

Addresses-Coverity-ID: 1056806

Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>