USB: ci13xxx_msm: shutdown callback to disable D+ pullup

SW reset may not reset the PHY properly by disabling
the D+ pullup.

Implement a shutdown callback to disable the pullup
during soft reboot so that host controller does
not go in bad state.

CRs-Fixed: 616180
Change-Id: I7bc76efdf78009a5e3705c049abd3678dc966885
Signed-off-by: Sujeet Kumar <ksujeet@codeaurora.org>
Signed-off-by: ChandanaKishori Chiluveru <cchilu@codeaurora.org>