soc/arm/microchip_mec/mec1501: Initialise GPIO after interrupts

Since bb590b5b, which enforces a more consistent ordering of
initialisation for devices, the SOC initialisation was happening after
GPIO initialisation. This caused interrupts to stop working on GPIO
input.

This patch fixes that by increasing the default GPIO initialisation
priority, so that it happens after SOC.

Signed-off-by: Ederson de Souza <ederson.desouza@intel.com>