mfd: Fix mismatch in twl4030 mutex lock-unlock

A mutex is locked on entry into twl4030_madc_conversion().
Immediate return on some error conditions leaves the
mutex locked.

This patch ensures that mutex is always unlocked before
leaving the function.
Signed-off-by: Sanjeev Premi <premi@ti.com>
Cc: Keerthy <j-keerthy@ti.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>

drivers/mfd/twl4030-madc.c

@@ -530,13 +530,13 @@ int twl4030_madc_conversion(struct twl4030_madc_request *req)
 	if (ret) {
 		dev_err(twl4030_madc->dev,
 			"unable to write sel register 0x%X\n", method->sel + 1);
-		return ret;
+		goto out;
 	}
 	ret = twl_i2c_write_u8(TWL4030_MODULE_MADC, ch_lsb, method->sel);
 	if (ret) {
 		dev_err(twl4030_madc->dev,
 			"unable to write sel register 0x%X\n", method->sel + 1);
-		return ret;
+		goto out;
 	}
 	/* Select averaging for all channels if do_avg is set */
 	if (req->do_avg) {
@@ -546,7 +546,7 @@ int twl4030_madc_conversion(struct twl4030_madc_request *req)
 			dev_err(twl4030_madc->dev,
 				"unable to write avg register 0x%X\n",
 				method->avg + 1);
-			return ret;
+			goto out;
 		}
 		ret = twl_i2c_write_u8(TWL4030_MODULE_MADC,
 				       ch_lsb, method->avg);
@@ -554,7 +554,7 @@ int twl4030_madc_conversion(struct twl4030_madc_request *req)
 			dev_err(twl4030_madc->dev,
 				"unable to write sel reg 0x%X\n",
 				method->sel + 1);
-			return ret;
+			goto out;
 		}
 	}
 	if (req->type == TWL4030_MADC_IRQ_ONESHOT && req->func_cb != NULL) {