regulator: core: Avoid device name duplication in NORMAL_GET

With current code:
	st-gyro-i2c i2c-PRP0001:00: i2c-PRP0001:00 supply vdd not found, using dummy regulator

which looks a bit oververbose.

Replace this with simplified format string for the above case, and drop
"deviceless" case since for all dev_*() macros used in _regulator_get()
the "(null)" will be printed anyway.
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20200312183245.1612-1-andriy.shevchenko@linux.intel.comSigned-off-by: Mark Brown <broonie@kernel.org>

drivers/regulator/core.c

@@ -1849,7 +1849,6 @@ struct regulator *_regulator_get(struct device *dev, const char *id,
 {
 	struct regulator_dev *rdev;
 	struct regulator *regulator;
-	const char *devname = dev ? dev_name(dev) : "deviceless";
 	struct device_link *link;
 	int ret;
 
@@ -1887,9 +1886,7 @@ struct regulator *_regulator_get(struct device *dev, const char *id,
 			 * enabled, even if it isn't hooked up, and just
 			 * provide a dummy.
 			 */
-			dev_warn(dev,
-				 "%s supply %s not found, using dummy regulator\n",
-				 devname, id);
+			dev_warn(dev, "supply %s not found, using dummy regulator\n", id);
 			rdev = dummy_regulator_rdev;
 			get_device(&rdev->dev);
 			break;