SVM range may includes multiple VMAs with different vm_flags, if prange
page index is the last page of the VMA offset + npages, update GPU
mapping to create GPU page table with same VMA access permission.

Signed-off-by: Philip Yang <Philip.Yang@amd.com>
Reviewed-by: Felix Kuehling <Felix.Kuehling@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>