musb: add host-mode sunxi support

This patch adds preliminary host-mode SUNXI support to MUSB OTG driver.

Things do not works correctly yet; there are problems with VBUS handling so
USB devices are not working stably yet.

Notes:
 - musb and sw_usb are based on same codebase.
 - sw_usb has DMA code disabled and PIO only mode is used.
 - Allwinner/sunxi musb register offsets are different from Texas Instruments'.
   Currently this is not problem, as musb only supports one "Platform Glue
   Layer" at a time (see ifdefs in current code). If multiarch is added to
   musb, musb needs to be changed to support different register mappings on
   runtime.

not-yet-signed-off-by: Jussi Kivilinna <jussi.kivilinna@iki.fi>