drm/amdgpu: Fix comparison in amdgpu_res_cpu_visible

drm/amdgpu: Fix comparison in amdgpu_res_cpu_visible

It incorrectly claimed a resource isn't CPU visible if it's located at
the very end of CPU visible VRAM.

Fixes: a6ff969fe9cb ("drm/amdgpu: fix visible VRAM handling during faults")
Closes: https://gitlab.freedesktop.org/drm/amd/-/issues/3343
Reviewed-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Reported-and-Tested-by: Jeremy Day <jsday@noreason.ca>
Signed-off-by: Michel Dänzer <mdaenzer@redhat.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
CC: stable@vger.kernel.org