spl: ram: Fix u_boot_pos calculation

The patch:
"spl: Weed out CONFIG_SYS_TEXT_BASE usage"
(sha1: 04ce5427bd)
introduced bug where assigning to u_boot_pos variable wasn't done
which end up in situation where SPL wasn't able to find out
image on the selected address.

Signed-off-by: Michal Simek <michal.simek@xilinx.com>

common/spl/spl_ram.c

@@ -63,9 +63,8 @@ static int spl_ram_load_image(struct spl_image_info *spl_image,
 			 * No binman support or no information. For now, fix it
 			 * to the address pointed to by U-Boot.
 			 */
-			header = spl_get_load_buffer(-sizeof(*header),
-						     sizeof(*header));
-
+			u_boot_pos = (ulong)spl_get_load_buffer(-sizeof(*header),
+								sizeof(*header));
 		}
 		header = (struct image_header *)map_sysmem(u_boot_pos, 0);