media: i2c: ov9650: fix potential integer overflow in __ov965x_set_frame_interval

Cast fi->interval.numerator to u64 in order to avoid a potential integer
overflow. This variable is being used in a context that expects an
expression of type u64.

Addresses-Coverity-ID: 1324146 ("Unintentional integer overflow")
[Sakari Ailus: use do_div() to make this work on 32-bit systems]

Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>