drm/amd/display: Fix spelling mistake of function name

There are two spelling mistakes of the function name, fix this
by using __func__ instead of a hard coded name string.

Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>