drm/radeon: allocate PPLLs from low to high

The order shouldn't matter, but there have been problems
reported on certain older asics.  This behaves more
like the original code before the PPLL allocation
rework.
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc:  Markus Trippelsdorf <markus@trippelsdorf.de>

drivers/gpu/drm/radeon/atombios_crtc.c

@@ -1690,10 +1690,10 @@ static int radeon_atom_pick_pll(struct drm_crtc *crtc)
 		}
 		/* all other cases */
 		pll_in_use = radeon_get_pll_use_mask(crtc);
-		if (!(pll_in_use & (1 << ATOM_PPLL2)))
-			return ATOM_PPLL2;
 		if (!(pll_in_use & (1 << ATOM_PPLL1)))
 			return ATOM_PPLL1;
+		if (!(pll_in_use & (1 << ATOM_PPLL2)))
+			return ATOM_PPLL2;
 		DRM_ERROR("unable to allocate a PPLL\n");
 		return ATOM_PPLL_INVALID;
 	} else {
@@ -1715,10 +1715,10 @@ static int radeon_atom_pick_pll(struct drm_crtc *crtc)
 			}
 			/* all other cases */
 			pll_in_use = radeon_get_pll_use_mask(crtc);
-			if (!(pll_in_use & (1 << ATOM_PPLL2)))
-				return ATOM_PPLL2;
 			if (!(pll_in_use & (1 << ATOM_PPLL1)))
 				return ATOM_PPLL1;
+			if (!(pll_in_use & (1 << ATOM_PPLL2)))
+				return ATOM_PPLL2;
 			DRM_ERROR("unable to allocate a PPLL\n");
 			return ATOM_PPLL_INVALID;
 		} else {