drm/nv50/pm: fix a typo in clock calculation

Signed-off-by: Martin Peres <[e-mail]>
Signed-off-by: Ben Skeggs <[e-mail]>

drivers/gpu/drm/nouveau/nv50_pm.c

···
 			case 0x00000800:
 				return read_clk(dev, clk_src_hclkm3d2) >> P;
 			case 0x00000c00:
-				return read_pll(dev, clk_src_mclk) >> P;
+				return read_clk(dev, clk_src_mclk) >> P;
 			}
 			break;
 		}