regulator: Restore L: linux-kernel@vger.kernel.org entry

As with commit 981c3a4f (MAINTAINERS: Restore "L:
linux-kernel@vger.kernel.org" entries) restore the mailing list entry
for the regulator framework in order to assist users in finding the list
if they read the file instead of using get_maintainers.pl.
Signed-off-by: Mark Brown <broonie@linaro.org>

MAINTAINERS

@@ -9827,6 +9827,7 @@ F:	drivers/scsi/vmw_pvscsi.h
 VOLTAGE AND CURRENT REGULATOR FRAMEWORK
 M:	Liam Girdwood <lgirdwood@gmail.com>
 M:	Mark Brown <broonie@kernel.org>
+L:	linux-kernel@vger.kernel.org
 W:	http://opensource.wolfsonmicro.com/node/15
 W:	http://www.slimlogic.co.uk/?p=48
 T:	git git://git.kernel.org/pub/scm/linux/kernel/git/broonie/regulator.git