drm/radeon: check firmware overrides for mclk/sclk ss

Check the overrides in the firmware info table before
enabling spread spectrum on the engine or memory clocks.

Some boards may have valid spread spectrum tables, but
shouldn't necessarily have it enabled.
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/radeon/radeon_atombios.c

@@ -1480,6 +1480,15 @@ bool radeon_atombios_get_asic_ss_info(struct radeon_device *rdev,
 	uint8_t frev, crev;
 	int i, num_indices;
 
+	if (id == ASIC_INTERNAL_MEMORY_SS) {
+		if (!(rdev->mode_info.firmware_flags & ATOM_BIOS_INFO_MEMORY_CLOCK_SS_SUPPORT))
+			return false;
+	}
+	if (id == ASIC_INTERNAL_ENGINE_SS) {
+		if (!(rdev->mode_info.firmware_flags & ATOM_BIOS_INFO_ENGINE_CLOCK_SS_SUPPORT))
+			return false;
+	}
+
 	memset(ss, 0, sizeof(struct radeon_atom_ss));
 	if (atom_parse_data_header(mode_info->atom_context, index, &size,
 				   &frev, &crev, &data_offset)) {