drm/amd/display: Use kernel alloc/free

Abstractions are frowned upon.

cocci script:
virtual context
virtual patch
virtual org
virtual report

@@
expression ptr;
@@

- dm_alloc(ptr)
+ kzalloc(ptr, GFP_KERNEL)

@@
expression ptr, size;
@@

- dm_realloc(ptr, size)
+ krealloc(ptr, size, GFP_KERNEL)

@@
expression ptr;
@@

- dm_free(ptr)
+ kfree(ptr)

v2: use GFP_KERNEL, not GFP_ATOMIC. add cocci script

Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>