MAINTAINERS: update arm64 Microchip entries

Krzysztof noticed that patches for arch/arm64/boot/dts/microchip were
getting lost & the listed tree was inactive.

Nicolas and I are willing to shepherd patches to Arnd, using the
existing at91 tree, so add a new entry covering
arch/arm64/boot/dts/microchip, listing us as maintainers.

Drop the tree from the existing sparx5 entry & narrow the devicetree
pattern to just sparx devices, leaving Lars, Steen and Daniel looking
after support for their SoCs.

CC: Rob Herring <robh+dt@kernel.org>
CC: Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>
CC: Conor Dooley <conor@kernel.org>
CC: Nicolas Ferre <nicolas.ferre@microchip.com>
CC: Claudiu Beznea <claudiu.beznea@microchip.com>
CC: soc@kernel.org
CC: Lars Povlsen <lars.povlsen@microchip.com>
CC: Steen Hegelund <Steen.Hegelund@microchip.com>
CC: Daniel Machon <daniel.machon@microchip.com>
Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
Acked-by: Nicolas Ferre <nicolas.ferre@microchip.com>
Acked-by: Steen Hegelund <Steen.Hegelund@microchip.com>
Acked-by: Claudiu Beznea <claudiu.beznea@microchip.com>
Link: https://lore.kernel.org/r/20230522-wagon-stencil-a164ec39322a@wendySigned-off-by: Arnd Bergmann <arnd@arndb.de>

MAINTAINERS

@@ -2429,6 +2429,15 @@ X:	drivers/net/wireless/atmel/
 N:	at91
 N:	atmel
 
+ARM/MICROCHIP (ARM64) SoC support
+M:	Conor Dooley <conor@kernel.org>
+M:	Nicolas Ferre <nicolas.ferre@microchip.com>
+M:	Claudiu Beznea <claudiu.beznea@microchip.com>
+L:	linux-arm-kernel@lists.infradead.org (moderated for non-subscribers)
+S:	Supported
+T:	git https://git.kernel.org/pub/scm/linux/kernel/git/at91/linux.git
+F:	arch/arm64/boot/dts/microchip/
+
 ARM/Microchip Sparx5 SoC support
 M:	Lars Povlsen <lars.povlsen@microchip.com>
 M:	Steen Hegelund <Steen.Hegelund@microchip.com>
@@ -2436,8 +2445,7 @@ M:	Daniel Machon <daniel.machon@microchip.com>
 M:	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/
+F:	arch/arm64/boot/dts/microchip/sparx*
 F:	drivers/net/ethernet/microchip/vcap/
 F:	drivers/pinctrl/pinctrl-microchip-sgpio.c
 N:	sparx5