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

Commit 3e457371 ("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: 3e457371 ("usb: musb: Fix fifo reads for dm816x with musb_dsps")
Reported-by: Fengguang Wu <fengguang.wu@intel.com>
Cc: Bin Liu <binmlist@gmail.com>
Cc: Brian Hutchinson <b.hutchman@gmail.com>
Cc: George Cherian <george.cherian@ti.com>
Cc: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>