usb: phy-msm-usb: Add enhancements to OTG driver debug logging

1. Add debug buffer logging in OTG driver which is not currently
supported. This helps to debug the device crash issues.

To disable debug buffer logging
echo 0 > /sys/module/phy_msm_usb/parameters/enable_dbg_log

2. Add debug events which track the pm_runtime_get/get_sync
and pm_runtime_put/put_sync calls. This helps to debug race
conditions occurring during PM runtime and system suspend/resume.

3. Introduce ->dbg_event() method  in usb_phy and add a function
interface to allow USB controllers to call on PHY to do specific
logging. This provides a callback method to add otg debug
logging from the controller drivers.

Change-Id: I9e950ec6a726e94066c347877394ac77d34af8f0
Signed-off-by: ChandanaKishori Chiluveru <cchilu@codeaurora.org>