regmap: Remove incorrect unreachable comment in regcache_set_val()

regcache_set_val() returns false if cache[idx] != val.
Thus it actually is not unreachable.

Signed-off-by: Axel Lin <axel.lin@gmail.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>

drivers/base/regmap/regcache.c

@@ -375,7 +375,6 @@ bool regcache_set_val(void *base, unsigned int idx,
 	default:
 		BUG();
 	}
-	/* unreachable */
 	return false;
 }