arm64: defconfig: Enable vWDT support to SVM

Enable vWDT support to SVM. Now SVM start pet the vWDT for a configured
pet time. If there are issues on SVM vWDT fires and eventually it barks
and take the whole system down to download mode to collect logs.

Change-Id: I861662f1d505d74937e0cc123875c34f530b128d
Signed-off-by: Murali Nalajala <mnalajal@codeaurora.org>