drm/amd/display: Add NULL check for kzalloc in 'amdgpu_dm_atomic_commit_tail()'

Add a NULL check for the kzalloc call that allocates memory for
dummy_updates in the amdgpu_dm_atomic_commit_tail function. Previously,
if kzalloc failed to allocate memory and returned NULL, the code would
attempt to use the NULL pointer.

The fix is to check if kzalloc returns NULL, and if so, log an error
message and skip the rest of the current loop iteration with the
continue statement.  This prevents the code from attempting to use the
NULL pointer.

Cc: Julia Lawall <julia.lawall@inria.fr>
Cc: Aurabindo Pillai <aurabindo.pillai@amd.com>
Cc: Rodrigo Siqueira <rodrigo.siqueira@amd.com>
Cc: Alex Hung <alex.hung@amd.com>
Cc: Alex Deucher <alexander.deucher@amd.com>
Reported-by: Julia Lawall <julia.lawall@inria.fr>
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/r/202401300629.ICnCt983-lkp@intel.com/


Fixes: 135fd1b3 ("drm/amd/display: Reduce stack size")
Signed-off-by: Srinivasan Shanmugam <srinivasan.shanmugam@amd.com>
Reviewed-by: Aurabindo Pillai <aurabindo.pillai@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>