MAINTAINERS: Add git tree for Sparx5

This adds a git tree for maintaining the Sparx5 SoC from.

Signed-off-by: Lars Povlsen <lars.povlsen@microchip.com>
Link: https://lore.kernel.org/r/20200914083257.11080-1-lars.povlsen@microchip.com

MAINTAINERS

@@ -2136,6 +2136,7 @@ M:	Steen Hegelund <Steen.Hegelund@microchip.com>
 M:	Microchip Linux Driver Support <UNGLinuxDriver@microchip.com>
 L:	linux-arm-kernel@lists.infradead.org (moderated for non-subscribers)
 S:	Supported
+T:	git git://github.com/microchip-ung/linux-upstream.git
 F:	arch/arm64/boot/dts/microchip/
 N:	sparx5