bootm: Support load images when os is elf

This extends the bootm command to allow find images when os type is elf.

Signed-off-by: Niu Zhihong <zone.niuzh@hotmail.com>
diff --git a/boot/bootm.c b/boot/bootm.c
index 854ac7e..f5cbb10 100644
--- a/boot/bootm.c
+++ b/boot/bootm.c
@@ -545,7 +545,8 @@
 	     images.os.type == IH_TYPE_KERNEL_NOLOAD ||
 	     images.os.type == IH_TYPE_MULTI) &&
 	    (images.os.os == IH_OS_LINUX || images.os.os == IH_OS_VXWORKS ||
-	     images.os.os == IH_OS_EFI || images.os.os == IH_OS_TEE)) {
+	     images.os.os == IH_OS_EFI || images.os.os == IH_OS_TEE ||
+	     images.os.os == IH_OS_ELF)) {
 		return bootm_find_images(img_addr, conf_ramdisk, conf_fdt, 0,
 					 0);
 	}