drm/amdkfd: optimize svm range evict

It is to avoid unnecessary queue eviction when range
is not mapped to gpu.

Signed-off-by: Eric Huang <jinhuieric.huang@amd.com>
Reviewed-by: Felix Kuehling <Felix.Kuehling@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>