defconfig: enable LINK_LAYER_TEST and EHSET_TEST on SM6150

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

Change-Id: Id6ade17aa03ed0358005e5921478eac7bec344ce
Signed-off-by: Pratham Pratap <prathampratap@codeaurora.org>