drm/amdgpu: Fix incorrect VRAM GART mappings on non-4K page size systems

drm/amdgpu: Fix incorrect VRAM GART mappings on non-4K page size systems

When mapping VRAM pages into the GART page table,
amdgpu_gart_map_vram_range() assumes that the system page size is the
same as the GPU page size.

On systems with non-4K page sizes, multiple GPU pages can exist within
a single CPU page. As a result, the mappings are created incorrectly
because fewer page table entries are programmed than required.

Fix this by programming the mappings correctly for non-4K page size
systems.

Fixes: 237d623ae659 ("drm/amdgpu/gart: Add helper to bind VRAM pages (v2)")
Reviewed-by: Timur Kristóf <timur.kristof@gmail.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Donet Tom <donettom@linux.ibm.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>