[media] smiapp: Use of_property_read_u64_array() to read a 64-bit number array

of_property_read_u64_array() wasn't yet part of the kernel tree when the
functionality was needed. Do use it now.

Signed-off-by: Sakari Ailus <sakari.ailus@iki.fi>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>