MAINTAINERS: add N: px5 regex to ARM ROCKCHIP

PX5 is a Rockchip SoC, so let's match *anything* in U-Boot which
contains this string in the path. However, this matches a bit too much,
specifically the PPC-based kmsupx5_defconfig so we need to exclude it
explicitly.

Reviewed-by: Heiko Stuebner <heiko@sntech.de>
Link: https://patch.msgid.link/20260707-rk-custodian-v1-4-dbc9c696e613@0leil.net
Signed-off-by: Quentin Schulz <u-boot@0leil.net>

MAINTAINERS

@@ -559,7 +559,10 @@ M:	Philipp Tomsich <philipp.tomsich@vrull.eu>
 M:	Kever Yang <kever.yang@rock-chips.com>
 S:	Maintained
 T:	git https://source.denx.de/u-boot/custodians/u-boot-rockchip.git
+# Exclude from N: px5 matches
+X:	configs/kmsupx5_defconfig
 N:	px30
+N:	px5
 N:	rockchip
 F:	arch/arm/dts/rk3*
 F:	arch/arm/dts/rv11*