USB: gadget: f_mtp: Fix problems transferring files from device to host

Exit from send_file_work immediately when a cancel request is received.

Only busy status if there is a cancel pending that has not been repoorted to userspace.
This avoids a race condition that can occur when mtp_read resets the state
to STATE_BUSY before we report status OK back to the host.

Change-Id: I73b70976b3df7e18ac886418aa3ccd013dc43085
Signed-off-by: Mike Lockwood <lockwood@android.com>
Signed-off-by: Chandra Devireddy <cdevired@codeaurora.org>
[cvelempa@codeaurora.org: Fix trivial merge conflict]
Signed-off-by: Chiranjeevi Velempati <cvelempa@codeaurora.org>
Merge "USB: gadget: f_mtp: Fix problems transferring files from device to host" into android-msm-2.6.32