drm/prime: Support page array >= 4GB

Without unsigned long typecast, the size is passed in as zero if page
array size >= 4GB, nr_pages >= 0x100000, then sg list converted will
have the first and the last chunk lost.

Signed-off-by: Philip Yang <Philip.Yang@amd.com>
Acked-by: Felix Kuehling <Felix.Kuehling@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
CC: stable@vger.kernel.org
Signed-off-by: Christian König <christian.koenig@amd.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230821200201.24685-1-Philip.Yang@amd.com