usb: musb: force PIO-only if we're building multiplatform kernels

MUSB still needs lots of work on the DMA part
if we want to enable multiple DMA engines on
a multiplatform kernel. Meanwhile, we're forcing
PIO-only so that we, at least, have a working
driver.
Signed-off-by: Felipe Balbi <balbi@ti.com>

drivers/usb/musb/Kconfig

@@ -67,6 +67,7 @@ endchoice
 
 choice
 	prompt 'MUSB DMA mode'
+	default MUSB_PIO_ONLY if ARCH_MULTIPLATFORM
 	default USB_UX500_DMA if USB_MUSB_UX500
 	default USB_INVENTRA_DMA if USB_MUSB_OMAP2PLUS || USB_MUSB_BLACKFIN
 	default USB_TI_CPPI_DMA if USB_MUSB_DAVINCI