hw/intc/aspeed: Set impl.min_access_size to 4

hw/intc/aspeed: Set impl.min_access_size to 4

This patch explicitly sets ".impl.min_access_size = 4" to match the
declared ".valid.min_access_size = 4", enforcing stricter access size
checking and preventing inconsistent partial accesses to the interrupt
controller registers.

Signed-off-by: Jamin Lin <jamin_lin@aspeedtech.com>
Reviewed-by: Cédric Le Goater <clg@redhat.com>
Link: https://lore.kernel.org/qemu-devel/20250522023305.2486536-2-jamin_lin@aspeedtech.com
Signed-off-by: Cédric Le Goater <clg@redhat.com>