USB: msm_defconfig: Enable EHCI driver for host mode

Enabling host mode on MSM8916 missed enabling the
EHCI driver in defconfig for 64 bit kernel. Because
of this, USB enumeration is not working. The reason
is that first time sm work is scheduled by
ehci probe in set_host.

Also, the PMIC notification handler returns without
scheduling sm work because ID is still clear.

To support hostmode and USB enumeration to work
on msm8916, enable it in its defconfig for 64-bit.

CRs-Fixed: 654054
Change-Id: Ib653a39e8433091b3c5da4abc020fb33286ce493
Signed-off-by: Sujeet Kumar <ksujeet@codeaurora.org>