arm64: defconfig: enable USB_LINK_LAYER_TEST on sdm845

Enable the LVS test driver which is used to validate USB
SuperSpeed link layer compliance when running against a
supported test system.

Change-Id: Id2cb8556ca6764a5839b90798c8bd619570b9b97
Signed-off-by: Jack Pham <jackp@codeaurora.org>