drm/amdgpu: Fix the memory allocation issue in amdgpu_discovery_get_nps_info()

Fix two issues with memory allocation in amdgpu_discovery_get_nps_info()
for mem_ranges:

 - Add a check for allocation failure to avoid dereferencing a null
   pointer.

 - As suggested by Christophe, use kvcalloc() for memory allocation,
   which checks for multiplication overflow.

Additionally, assign the output parameters nps_type and range_cnt after
the kvcalloc() call to prevent modifying the output parameters in case
of an error return.

Fixes: b194d21b ("drm/amdgpu: Use NPS ranges from discovery table")
Suggested-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Reviewed-by: Lijo Lazar <lijo.lazar@amd.com>
Signed-off-by: Li Huafei <lihuafei1@huawei.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>