Add missing include <plat/cpu.h> in drivers/mfd/omap-usb-host.c

Fix compilation error for omap boards (beagleboard, etc.) due to missing include <plat/cpu.h> in drivers/mfd/omap-usb-host.c leading to build error:
CC drivers/mfd/omap-usb-host.o
drivers/mfd/omap-usb-host.c: In function 'omap_usbhs_init':
drivers/mfd/omap-usb-host.c:524: error: implicit declaration of function 'cpu_is_omap3430'
drivers/mfd/omap-usb-host.c:524: error: implicit declaration of function 'omap_rev'
drivers/mfd/omap-usb-host.c:524: error: 'OMAP3430_REV_ES2_1' undeclared (first use in this function) drivers/mfd/omap-usb-host.c:524: error: (Each undeclared identifier is reported only once
drivers/mfd/omap-usb-host.c:524: error: for each function it appears in.)

---
KernelVersion: 3.4-rc5

  drivers/mfd/omap-usb-host.c |    1 +
  1 files changed, 1 insertions(+), 0 deletions(-)

index c8aae66..7e96bb2 100644
@@ -25,6 +25,7 @@
  #include <linux/clk.h>
  #include <linux/dma-mapping.h>
  #include <linux/spinlock.h>
+#include <plat/cpu.h>
  #include <plat/usb.h>
  #include <linux/pm_runtime.h>
 

1.7.7