usb: gadget: f_mtp: move userspace interface to uapi

Move the most of linux/usb/f_mtp.h header to uapi.  Move the only
remaining structure definition into f_mtp.c, the only place that
uses it.

Change-Id: I952c1a9dc15c36bf295a0eb4d74b6b1ad912ed03
Signed-off-by: Colin Cross <ccross@android.com>
Git-commit: 4d174ee19f31fd93f7f1d835bf7e2b613e399dad
Git-Repo: https://android.googlesource.com/kernel/common.git


Signed-off-by: Ian Maund <imaund@codeaurora.org>