ARM: dts: microchip: sam9x60: Remove additional compatible string from GPIO node

ARM: dts: microchip: sam9x60: Remove additional compatible string from GPIO node

The driver data specific to each pinctrl GPIO bank compatible nodes are not
the same and declaring additional compatible string as fallback has no
specific purpose, hence, removing the "atmel,at91sam9x5-gpio" compatible from
sam9x60 SoC DT.

Note: The at91 pinctrl driver uses "atmel,at91rm9200-gpio" compatible string
to find the number of active GPIO banks and identify the pinmux nodes.It
should used as a constant across all DT for GPIO node banks that uses PIO3
based pinctrl driver

Signed-off-by: Manikandan Muralidharan <manikandan.m@microchip.com>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Link: https://lore.kernel.org/r/20240814061315.112564-4-manikandan.m@microchip.com
Signed-off-by: Claudiu Beznea <claudiu.beznea@tuxon.dev>