sunxi: Use BROM stored boot_media value to determine our boot-source

Now that we know that the BROM stores a value indicating the boot-source
at the beginning of SRAM, use that instead of trying to recreate the
BROM's boot probing.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Ian Campbell <ijc@hellion.org.uk>
diff --git a/board/sunxi/board.c b/board/sunxi/board.c
index 320958a..f6e28b0 100644
--- a/board/sunxi/board.c
+++ b/board/sunxi/board.c
@@ -369,8 +369,7 @@
 	 * are searched there first. Note we only do this for u-boot proper,
 	 * not for the SPL, see spl_boot_device().
 	 */
-	if (!sunxi_mmc_has_egon_boot_signature(mmc0) &&
-	    sunxi_mmc_has_egon_boot_signature(mmc1)) {
+	if (readb(SPL_ADDR + 0x28) == SUNXI_BOOTED_FROM_MMC2) {
 		/* Booting from emmc / mmc2, swap */
 		mmc0->block_dev.devnum = 1;
 		mmc1->block_dev.devnum = 0;