drm/radeon/kms: pll tweaks for r7xx

Prefer min m to max p only on pre-r7xx asics.

Fixes:
https://bugs.freedesktop.org/show_bug.cgi?id=36197

Signed-off-by: Alex Deucher <alexdeucher@gmail.com>
Cc: stable@kernel.org
Signed-off-by: Dave Airlie <airlied@redhat.com>

drivers/gpu/drm/radeon/atombios_crtc.c

@@ -532,10 +532,7 @@ static u32 atombios_adjust_pll(struct drm_crtc *crtc,
 		else
 			pll->flags |= RADEON_PLL_PREFER_LOW_REF_DIV;
 
-		if ((rdev->family == CHIP_R600) ||
-		    (rdev->family == CHIP_RV610) ||
-		    (rdev->family == CHIP_RV630) ||
-		    (rdev->family == CHIP_RV670))
+		if (rdev->family < CHIP_RV770)
 			pll->flags |= RADEON_PLL_PREFER_MINM_OVER_MAXP;
 	} else {
 		pll->flags |= RADEON_PLL_LEGACY;
@@ -565,7 +562,6 @@ static u32 atombios_adjust_pll(struct drm_crtc *crtc,
 			if (radeon_encoder->devices & (ATOM_DEVICE_LCD_SUPPORT)) {
 				if (ss_enabled) {
 					if (ss->refdiv) {
-						pll->flags |= RADEON_PLL_PREFER_MINM_OVER_MAXP;
 						pll->flags |= RADEON_PLL_USE_REF_DIV;
 						pll->reference_div = ss->refdiv;
 						if (ASIC_IS_AVIVO(rdev))