drm/amdkfd: Fix memory leak in create_process failure

drm/amdkfd: Fix memory leak in create_process failure

Fix memory leak due to a leaked mmget reference on an error handling
code path that is triggered when attempting to create KFD processes
while a GPU reset is in progress.

Fixes: 0ab2d7532b05 ("drm/amdkfd: prepare per-process debug enable and disable")
CC: Xiaogang Chen <[email protected]>
Signed-off-by: Felix Kuehling <[email protected]>
Tested-by: Harish Kasiviswanthan <[email protected]>
Reviewed-by: Mukul Joshi <[email protected]>
Signed-off-by: Alex Deucher <[email protected]>
Cc: [email protected]