drm/amd/display: use GFP_ATOMIC in dcn20_resource_construct

Replace GFP_KERNEL with GFP_ATOMIC as dcn20_resource_construct()
can't sleep.

Partially fixes: https://bugzilla.kernel.org/show_bug.cgi?id=212311


as dcn20_resource_construct() also calls into SMU functions which does
mutex_lock().

Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Nirmoy Das <nirmoy.das@amd.com>