spl: sdp: Add CONFIG_SPL_SDP_USB_DEV for USB device

Add a new configuration CONFIG_SPL_SDP_USB_DEV to specify the
usb index for spl sdp driver, so that we change use different device.
The default value is 0.

Signed-off-by: Ye Li <ye.li@nxp.com>
Signed-off-by: Peng Fan <peng.fan@nxp.com>
diff --git a/common/spl/Kconfig b/common/spl/Kconfig
index 9feadb5..6f37f75 100644
--- a/common/spl/Kconfig
+++ b/common/spl/Kconfig
@@ -1172,6 +1172,14 @@
 	  Enable Serial Download Protocol (SDP) device support in SPL. This
 	  allows to download images into memory and execute (jump to) them
 	  using the same protocol as implemented by the i.MX family's boot ROM.
+
+config SPL_SDP_USB_DEV
+	int "SDP USB controller index"
+	default 0
+	depends on SPL_USB_SDP_SUPPORT
+	help
+	  Some boards have USB controller other than 0. Define this option
+	  so it can be used in compiled environment.
 endif
 
 config SPL_WATCHDOG_SUPPORT