arm: atmel: get rid of too many ifdeffery

Get rid of too many ifdeffery in usb ohci driver

Add following two configuration for USB clock selecting
- CONFIG_USB_ATMEL_CLK_SEL_PLLB: using PLLB as usb ohci input clock
- CONFIG_USB_ATMEL_CLK_SEL_UPLL: using UPLL as usb ohci input clock

Signed-off-by: Bo Shen <voice.shen@atmel.com>
Signed-off-by: Andreas Bießmann <andreas.devel@googlemail.com>
diff --git a/include/configs/stamp9g20.h b/include/configs/stamp9g20.h
index a997331..95fc26b 100644
--- a/include/configs/stamp9g20.h
+++ b/include/configs/stamp9g20.h
@@ -165,6 +165,7 @@
 
 /* USB configuration */
 #define CONFIG_USB_ATMEL
+#define CONFIG_USB_ATMEL_CLK_SEL_PLLB
 #define CONFIG_USB_OHCI_NEW
 #define CONFIG_USB_STORAGE
 #define CONFIG_DOS_PARTITION