target: mdm9607: support to enable/disable usb to save power.

USB will be disabled in SBL to save power during bootup in mdm9206,
with these changes enabling the USB LDO4 before going to fastboot.
USB will be disabled when booting to kernel.

Change-Id: I21958a15c860831a8eb8e82f389575afac91ad78
4 files changed