usb: renesas: fix scheduling in atomic context bug

The current renesas_usbhs driver triggers

BUG: scheduling while atomic: ksoftirqd/0/3/0x00000102

with enabled CONFIG_DEBUG_ATOMIC_SLEEP, by submitting DMA transfers from
an atomic (tasklet) context, which is not supported by the shdma dmaengine
driver. Fix it by switching to a work.

Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: Felipe Balbi <balbi@ti.com>

drivers/usb/renesas_usbhs/fifo.h

@@ -19,6 +19,7 @@
 
 #include <linux/interrupt.h>
 #include <linux/sh_dma.h>
+#include <linux/workqueue.h>
 #include <asm/dma.h>
 #include "pipe.h"
 
@@ -31,7 +32,6 @@ struct usbhs_fifo {
 	u32 ctr;	/* xFIFOCTR */
 
 	struct usbhs_pipe	*pipe;
-	struct tasklet_struct	tasklet;
 
 	struct dma_chan		*tx_chan;
 	struct dma_chan		*rx_chan;
@@ -53,6 +53,7 @@ struct usbhs_pkt {
 	struct usbhs_pkt_handle *handler;
 	void (*done)(struct usbhs_priv *priv,
 		     struct usbhs_pkt *pkt);
+	struct work_struct work;
 	dma_addr_t dma;
 	void *buf;
 	int length;