ARM: OMAP2+: Fix module build errors with CONFIG_OMAP4_ERRATA_I688

While building modules with randconfig the below errors are observed.

ERROR: "omap_bus_sync" [drivers/watchdog/sp805_wdt.ko] undefined!
ERROR: "omap_bus_sync" [drivers/watchdog/dw_wdt.ko] undefined!
ERROR: "omap_bus_sync" [drivers/virtio/virtio_ring.ko] undefined!
ERROR: "omap_bus_sync" [drivers/video/sm501fb.ko] undefined!
ERROR: "omap_bus_sync" [drivers/usb/mon/usbmon.ko] undefined!
ERROR: "omap_bus_sync" [drivers/usb/host/sl811-hcd.ko] undefined!
ERROR: "omap_bus_sync" [drivers/usb/host/ohci-hcd.ko] undefined!
ERROR: "omap_bus_sync" [drivers/usb/host/isp1760.ko] undefined!
ERROR: "omap_bus_sync" [drivers/usb/host/isp1362-hcd.ko] undefined!
ERROR: "omap_bus_sync" [drivers/usb/host/isp116x-hcd.ko] undefined!
ERROR: "omap_bus_sync" [drivers/usb/core/usbcore.ko] undefined!
ERROR: "omap_bus_sync" [drivers/tty/serial/altera_uart.ko] undefined!
ERROR: "omap_bus_sync" [drivers/tty/serial/altera_jtaguart.ko] undefined!
ERROR: "omap_bus_sync" [drivers/tty/serial/8250/8250_dw.ko] undefined!
ERROR: "omap_bus_sync" [drivers/ssb/ssb.ko] undefined!
ERROR: "omap_bus_sync" [drivers/rtc/rtc-cmos.ko] undefined!
ERROR: "omap_bus_sync" [drivers/rtc/rtc-bq4802.ko] undefined!
ERROR: "omap_bus_sync" [drivers/mtd/nand/tmio_nand.ko] undefined!
ERROR: "omap_bus_sync" [drivers/mtd/nand/omap2.ko] undefined!

Signed-off-by: R Sricharan <r.sricharan@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>