ARM: at91: select ARCH_MICROCHIP

Like with the ARM64 Microchip platforms, lets add a generic ARCH_MICROCHIP
symbol and select it so that drivers that are reused for multiple product
generation or lines, can just depend on it instead of adding each SoC
symbol as their dependencies.

Signed-off-by: Robert Marko <robert.marko@sartura.hr>
Acked-by: Nicolas Ferre <nicolas.ferre@microchip.com>
Acked-by: Daniel Machon <daniel.machon@microchip.com>
Link: https://lore.kernel.org/r/20250813174720.540015-3-robert.marko@sartura.hr
Signed-off-by: Claudiu Beznea <claudiu.beznea@tuxon.dev>
Signed-off-by: Nicolas Ferre <nicolas.ferre@microchip.com>

Author: robimarko

arch/arm/mach-at91/Kconfig

@@ -1,4 +1,7 @@
 # SPDX-License-Identifier: GPL-2.0-only
+config ARCH_MICROCHIP
+	bool
+
 menuconfig ARCH_AT91
 	bool "AT91/Microchip SoCs"
 	depends on (CPU_LITTLE_ENDIAN && (ARCH_MULTI_V4T || ARCH_MULTI_V5)) || \
@@ -8,6 +11,7 @@ menuconfig ARCH_AT91
 	select GPIOLIB
 	select PINCTRL
 	select SOC_BUS
+	select ARCH_MICROCHIP
 
 if ARCH_AT91
 config SOC_SAMV7