usb: musb: dsps: fix build on i386 when COMPILE_TEST is set

Commit 3e457371f436 ("usb: musb: Fix fifo reads for dm816x with musb_dsps")
fixed a USB error on dm816x, but introduced a new build error on i386
when COMPILE_TEST is set:

drivers/usb/musb/musb_dsps.c: In function ‘dsps_read_fifo32’:
drivers/usb/musb/musb_dsps.c:624:3: error: implicit declaration of function
‘readsl’ [-Werror=implicit-function-declaration]
readsl(fifo, dst, len >> 2);

Let's fix this by using ioread32_rep() instead of readsl() as that's
more portable.

Fixes: 3e457371f436 ("usb: musb: Fix fifo reads for dm816x with musb_dsps")
Reported-by: Fengguang Wu <[e-mail]>
Cc: Bin Liu <[e-mail]>
Cc: Brian Hutchinson <[e-mail]>
Cc: George Cherian <[e-mail]>
Cc: Sergei Shtylyov <[e-mail]>
Signed-off-by: Tony Lindgren <[e-mail]>
Signed-off-by: Felipe Balbi <[e-mail]>
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/usb/musb/musb_dsps.c

···
 	void __iomem *fifo = hw_ep->fifo;
 
 	if (len >= 4) {
-		readsl(fifo, dst, len >> 2);
+		ioread32_rep(fifo, dst, len >> 2);
 		dst += len & ~0x03;
 		len &= 0x03;
 	}