amdgpu: validate offset_in_bo of drm_amdgpu_gem_va

This is motivated by OOB access in amdgpu_vm_update_range when
offset_in_bo+map_size overflows.

v2: keep the validations in amdgpu_vm_bo_map
v3: add the validations to amdgpu_vm_bo_map/amdgpu_vm_bo_replace_map
    rather than to amdgpu_gem_va_ioctl

Fixes: 9f7eb536 ("drm/amdgpu: actually use the VM map parameters")
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Chia-I Wu <olvaffe@gmail.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>