microblaze: Add SPL support

Add support for U-BOOT SPL. NOR and RAM mode are supported.
There are 3 images in NOR flash. u-boot.img, dtb and kernel.

Signed-off-by: Michal Simek <michal.simek@xilinx.com>
diff --git a/arch/microblaze/include/asm/u-boot.h b/arch/microblaze/include/asm/u-boot.h
index 31b014c..ab3f232 100644
--- a/arch/microblaze/include/asm/u-boot.h
+++ b/arch/microblaze/include/asm/u-boot.h
@@ -25,6 +25,7 @@
 	unsigned long	bi_sramstart;	/* start of SRAM memory */
 	unsigned long	bi_sramsize;	/* size	 of SRAM memory */
 	unsigned int	bi_baudrate;	/* Console Baudrate */
+	ulong		bi_boot_params; /* where this board expects params */
 } bd_t;
 
 /* For image.h:image_check_target_arch() */