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: Ie36187aa963259e4d18e8dbbd2d6ee7ccea9ec3c
Signed-off-by: Chandana Kishori Chiluveru <cchiluve@codeaurora.org>