KGDB: Enable KGDB for Android using the msm72k_udc USB driver
Added new I/O functions to the gadget drivers to support KGDB.
The usb function f_acm.c and u_serial.c should be able to
communicate with gdb on the host PC. The changes support
concurrent use of the adb interface.

A new kgdb parameter kgdbretry=[delay] is added to kgdboc.c
to allow kgdb to retry the USB device specified in kgdboc when
it is initialized later in system boot. The [delay] value is
in seconds.

Forward-port from Linux 2.6 by cholokei

Signed-off-by: cholokei <leesl0416@naver.com>