drm/amd: Add missing definitions for `SMU_MAX_LEVELS_VDDGFX`

It is reported that on a Topaz dGPU the kernel emits:
	amdgpu: can't get the mac of 5

This is because there is no definition for max levels of VDDGFX
declared for SMU71 or SMU7. The correct definition is VDDC so
use this.

Link: https://gitlab.freedesktop.org/drm/amd/-/issues/3049


Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>