usb: musb: introduce api for dma code to check compatibility with usb request
Gadget MUSB driver handles dma mappings in musb_gadget_queue(). Where as it is
possible for dma code to reject the usb request later at ->channel_program()
called from txstate()/rxstate()
In this case, usb request will be handled in PIO mode which renders dma mapping
operations unnecessary.
This patch adds an api to allow dma code to indicate incompatibility with usb
request. Gadget musb driver call this api, if available, before dma mappings to
avoid any unnecessary mapping operations.
Signed-off-by: Mian Yousaf Kaukab <mian.yousaf.kaukab@stericsson.com> Signed-off-by: Felipe Balbi <balbi@ti.com>