drm/amdkfd: fixes for HMM mem allocation

Fix err return value and reset pgmap->type after checking it.

Fixes: c83dee9b

 ("drm/amdkfd: add SPM support for SVM")
Reviewed-by: Felix Kuehling <felix.kuehling@amd.com>
Signed-off-by: Dafna Hirschfeld <dhirschfeld@habana.ai>
Signed-off-by: Felix Kuehling <felix.kuehling@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>