SPL: Add struct spl_boot_device parameter into spl_parse_board_header()

Add parameter spl_boot_device to spl_parse_board_header(), which allows
the implementations to see from which device we are booting and do
boot-device-specific checks of the image header.

Signed-off-by: Pali Rohár <pali@kernel.org>
Signed-off-by: Marek Behún <marek.behun@nic.cz>
Reviewed-by: Stefan Roese <sr@denx.de>
diff --git a/common/spl/spl_net.c b/common/spl/spl_net.c
index d23b395..a853e6a 100644
--- a/common/spl/spl_net.c
+++ b/common/spl/spl_net.c
@@ -58,7 +58,7 @@
 	} else {
 		debug("Legacy image\n");
 
-		rv = spl_parse_image_header(spl_image, header);
+		rv = spl_parse_image_header(spl_image, bootdev, header);
 		if (rv)
 			return rv;