MAINTAINER: alpine: add a mailing list

Add the linux-arm-kernel mailing list for the Alpine SoCs.
Signed-off-by: Antoine Tenart <antoine.tenart@free-electrons.com>
Signed-off-by: Olof Johansson <olof@lixom.net>

MAINTAINERS

@@ -999,6 +999,7 @@ N:	meson
 ARM/Annapurna Labs ALPINE ARCHITECTURE
 M:	Tsahee Zidenberg <tsahee@annapurnalabs.com>
 M:	Antoine Tenart <antoine.tenart@free-electrons.com>
+L:	linux-arm-kernel@lists.infradead.org (moderated for non-subscribers)
 S:	Maintained
 F:	arch/arm/mach-alpine/
 F:	arch/arm/boot/dts/alpine*