drm/amd/display: Use kmalloc_array() instead of kmalloc()

drm/amd/display: Use kmalloc_array() instead of kmalloc()

Documentation/process/deprecated.rst recommends against the use of kmalloc
with dynamic size calculations due to the risk of overflow and smaller
allocation being made than the caller was expecting. This could lead to
buffer overflow in code similar to the memcpy in
amdgpu_dm_plane_add_modifier().

Signed-off-by: James Flowers <bold.zone2373@fastmail.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>