DMAEngine will be supported to this driver in the future.
Then, both PIO and DMA data transfer method should be supported.
But, the transfer function can returns the result immediately
in PIO version, but it can't in DMA version.
This patch divides data transfer functions into top/bottom half
in preparation for DMAEngine support.
Signed-off-by: NKuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

Current renesas_usbhs has PIO data transfer mode which controls CFIFO.
And it was implemented in pipe.c.
But, fifo control method needs more flexible implementation
to support DMAEngine.
This patch create fifo.c, and it became independent from pipe.c.
Signed-off-by: NKuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>