Enable i6300ESB watchdog driver for generic-aarch64

This is one of WDT drivers used by KVM/QEMU. For OVA it's been already enabled
in #2627 - enable it for aarch64 as well.

Fixes #3414

buildroot-external/board/arm-uefi/generic-aarch64/kernel.config

@@ -55,3 +55,5 @@ CONFIG_HYPERV_VSOCKETS=m
 CONFIG_PCI_HYPERV=m
 CONFIG_PCI_HYPERV_INTERFACE=m
 CONFIG_FB_HYPERV=y
+
+CONFIG_I6300ESB_WDT=y