fix build error for bf527-ezkit_defconfig for old silicon

Signed-off-by: Aaron Wu <Aaron.wu@analog.com>

fix build error for bf527-ezkit_defconfig for old silicon
diff --git a/arch/blackfin/configs/BF527-EZKIT_defconfig b/arch/blackfin/configs/BF527-EZKIT_defconfig
index 90b1753..af2738c 100644
--- a/arch/blackfin/configs/BF527-EZKIT_defconfig
+++ b/arch/blackfin/configs/BF527-EZKIT_defconfig
@@ -146,6 +146,7 @@
 CONFIG_USB_OTG_BLACKLIST_HUB=y
 CONFIG_USB_MON=y
 CONFIG_USB_MUSB_HDRC=y
+CONFIG_MUSB_PIO_ONLY=y
 CONFIG_USB_MUSB_BLACKFIN=y
 CONFIG_MUSB_PIO_ONLY=y
 CONFIG_USB_STORAGE=y