MAINTAINERS: Add reviewer for regulator irq_helpers

Add a reviewer entry for the regulator irq_helpers.
Signed-off-by: NMatti Vaittinen <matti.vaittinen@fi.rohmeurope.com>
Link: https://lore.kernel.org/r/2a4286ed98fd69b2539919e6a3e84d2e9804b4da.1622628334.git.matti.vaittinen@fi.rohmeurope.comSigned-off-by: NMark Brown <broonie@kernel.org>

MAINTAINERS

@@ -19566,6 +19566,10 @@ F:	include/dt-bindings/regulator/
 F:	include/linux/regulator/
 K:	regulator_get_optional
 
+VOLTAGE AND CURRENT REGULATOR IRQ HELPERS
+R:	Matti Vaittinen <matti.vaittinen@fi.rohmeurope.com>
+F:	drivers/regulator/irq_helpers.c
+
 VRF
 M:	David Ahern <dsahern@kernel.org>
 L:	netdev@vger.kernel.org