defconfig: Enable EHSET Test Fixture device driver for sdxpoorwills

Enable required EHSET Test fixture driver to perform the high speed
electrical testing procedure for USB-IF compliance for sdx24.

Change-Id: Ib5b0936c524ee5ea46da9e9d451bbc02f8522783
Signed-off-by: Chandana Kishori Chiluveru <cchiluve@codeaurora.org>