defconfig: sdm670: Enable VT config for arm64

Wayland/Weston support requires tty functionality since Weston server
protocol gets requests from various tty shells.

So, enable CONFIG_VT both for perf and non-perf defconfig of sdm670.

Change-Id: I8c0f497a19468fd7e6cd6ae7fe87787c8cb12e01
Signed-off-by: Mukesh Ojha <mojha@codeaurora.org>