usb: gadget: Add snapshot of f_fs changes from msm-3.10

Squash and apply the following f_fs function driver changes taken
from the msm-3.10 kernel branch as of msm-3.10 commit
f62f95b715a5   (Merge "dwc3-msm: Turn on 1.8V LDO before turning on
		3.3V LDO")

324e676 USB: f_fs: Set ffs->func to NULL after disabling endpoint in
	set_alt()
b20795b usb: gadget: f_fs: Reuse string indexes when possible
b6049f7 USB: gadget: Compilation fixes for 64-bit support
70d8266 USB: gagget: f_fs: Return error if TX req is queued during device
	offline
862bbca USB: gadget: f_fs: Release endpoint upon disable
8e712e5 USB: f_fs: Fix epfile crash during composition switch
2e61163 USB: f_fs: Fail stale read IOs after disconnect
d288cda USB: f_fs: Cutoff epfile IO before epfile could get freed
6ed8bf3 USB: f_fs: Check error status before doing epfile I/O
4954332 USB: f_fs: Fix disconnect check during ongoing IO
44f86b5 USB: f_fs: Move ep completion out of stack
ff57986 usb: gadget: f_fs: Allow only one adb daemon perform device open

Change-Id: I44597b463dd26ec139964e0a65a47273ef1dcd11
Signed-off-by: Tarun Gupta <tarung@codeaurora.org>