drm/amdgpu: update docum. filename following rename

Fix documentation build errors for amdgpu: correct the filename.

Error: Cannot open file ../drivers/gpu/drm/amd/amdgpu/amdgpu_mn.c
Error: Cannot open file ../drivers/gpu/drm/amd/amdgpu/amdgpu_mn.c
Error: Cannot open file ../drivers/gpu/drm/amd/amdgpu/amdgpu_mn.c

WARNING: kernel-doc '../scripts/kernel-doc -rst -enable-lineno -sphinx-version 5.3.0 -function MMU Notifier ../drivers/gpu/drm/amd/amdgpu/amdgpu_mn.c' failed with return code 1
WARNING: kernel-doc '../scripts/kernel-doc -rst -enable-lineno -sphinx-version 5.3.0 -internal ../drivers/gpu/drm/amd/amdgpu/amdgpu_mn.c' failed with return code 2

Fixes: d9483ec ("drm/amdgpu: rename the files for HMM handling")
Signed-off-by: Randy Dunlap <[email protected]>
Cc: Christian König <[email protected]>
Cc: Alex Deucher <[email protected]>
Cc: Felix Kuehling <[email protected]>
Cc: David Airlie <[email protected]>
Cc: Daniel Vetter <[email protected]>
Cc: Jonathan Corbet <[email protected]>
Cc: [email protected]
Cc: [email protected]
Signed-off-by: Alex Deucher <[email protected]>

Author: rddunlap

Documentation/gpu/amdgpu/driver-core.rst

@@ -148,10 +148,10 @@ PRIME Buffer Sharing
 MMU Notifier
 ============
 
-.. kernel-doc:: drivers/gpu/drm/amd/amdgpu/amdgpu_mn.c
+.. kernel-doc:: drivers/gpu/drm/amd/amdgpu/amdgpu_hmm.c
    :doc: MMU Notifier
 
-.. kernel-doc:: drivers/gpu/drm/amd/amdgpu/amdgpu_mn.c
+.. kernel-doc:: drivers/gpu/drm/amd/amdgpu/amdgpu_hmm.c
    :internal:
 
 AMDGPU Virtual Memory