USB: gadget: Implement COMPAT_IOCTL for ioctls

32-bit userspace calling into 64-bit kernel
cause different ioctl codes to get generated.
The different ioctl code gets generated
because sizeof is used on mtp and accessory
structures which is different for 32/64
compilation. Because of this, 64-bit kernel
can never execute the right ioctl command.

Implement compat_ioctl to handle such
execution environment.

CRs-Fixed: 678625
Change-Id: I26cc10986e28a28eab6f3c65f28f4d2b808112d9
Signed-off-by: Sujeet Kumar <ksujeet@codeaurora.org>