drm/amd/amdkfd: Fix a resource leak in svm_range_validate_and_map()

Analysis of code by Coverity, a static code analyser, has identified
a resource leak in the symbol hmm_range. This leak occurs when one of
the prior steps before it is released encounters an error.

Signed-off-by: Ramesh Errabolu <Ramesh.Errabolu@amd.com>
Reviewed-by: Felix Kuehling <felix.kuehling@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>