MAINTAINERS: Add maintainer entry for linear ranges helper

The linear ranges helpers were refactored out of regulator core
for other drivers to enjoy. Add regulator maintainer Mark Brown as
maintainer and myself as a reviewer.
Signed-off-by: Matti Vaittinen <matti.vaittinen@fi.rohmeurope.com>
Link: https://lore.kernel.org/r/fbbbee249c6b9df3ba63bb51ea53526b22921e84.1589866138.git.matti.vaittinen@fi.rohmeurope.comSigned-off-by: Mark Brown <broonie@kernel.org>

MAINTAINERS

@@ -9720,6 +9720,13 @@ F:	drivers/lightnvm/
 F:	include/linux/lightnvm.h
 F:	include/uapi/linux/lightnvm.h
 
+LINEAR RANGES HELPERS
+M:	Mark Brown <broonie@kernel.org>
+R:	Matti Vaittinen <matti.vaittinen@fi.rohmeurope.com>
+F:	lib/linear_ranges.c
+F:	lib/test_linear_ranges.c
+F:	include/linux/linear_range.h
+
 LINUX FOR POWER MACINTOSH
 M:	Benjamin Herrenschmidt <benh@kernel.crashing.org>
 L:	linuxppc-dev@lists.ozlabs.org