power: smb1398: Handle USB power path suspension appropriately

Unsuspend USB power path (turn off USB-path front-porch FET) before
enabling, and suspend it upon disabling SMB1398.

Change-Id: I319c215861f82cb2fb96504c38993c6eb03c38a7
Signed-off-by: Guru Das Srinagesh <gurus@codeaurora.org>