drm/radeon: add SI DPM quirk for Sapphire R9 270 Dual-X 2G GDDR5

Seems to have problems with high mclks.

bug:
https://bugs.freedesktop.org/show_bug.cgi?id=76490Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org

drivers/gpu/drm/radeon/si_dpm.c

@@ -2924,6 +2924,7 @@ struct si_dpm_quirk {
 static struct si_dpm_quirk si_dpm_quirk_list[] = {
 	/* PITCAIRN - https://bugs.freedesktop.org/show_bug.cgi?id=76490 */
 	{ PCI_VENDOR_ID_ATI, 0x6810, 0x1462, 0x3036, 0, 120000 },
+	{ PCI_VENDOR_ID_ATI, 0x6811, 0x174b, 0xe271, 0, 120000 },
 	{ 0, 0, 0, 0 },
 };