tools: kwbimage: Add constant for SDIO bootfrom

Add constant for SDIO value of the bootfrom header field.
Signed-off-by: NMarek Behún <marek.behun@nic.cz>
Reviewed-by: NStefan Roese <sr@denx.de>
Reviewed-by: NChris Packham <judge.packham@gmail.com>
Tested-by: NChris Packham <judge.packham@gmail.com>

tools/kwbimage.h

@@ -27,6 +27,7 @@
 #define IBR_HDR_SATA_ID			0x78
 #define IBR_HDR_PEX_ID			0x9C
 #define IBR_HDR_UART_ID			0x69
+#define IBR_HDR_SDIO_ID			0xAE
 #define IBR_DEF_ATTRIB	 		0x00
 
 /* Structure of the main header, version 0 (Kirkwood, Dove) */