boot: arm: riscv: sandbox: Add a format for the booti file

Arm invented a new format for arm64 and something similar is also used
with RISC-V. Add this to the list of supported formats and provide a way
for the format to be detected on both architectures.

Update the genimg_get_format() function to support this.

Fix up switch() statements which don't currently mention this format.
Booti does not support a ramdisk, so this can be ignored.

Signed-off-by: Simon Glass <sjg@chromium.org>

include/image.h

@@ -603,6 +603,7 @@ enum image_fmt_t {
 	IMAGE_FORMAT_LEGACY,		/* legacy image_header based format */
 	IMAGE_FORMAT_FIT,		/* new, libfdt based format */
 	IMAGE_FORMAT_ANDROID,		/* Android boot image */
+	IMAGE_FORMAT_BOOTI,		/* Arm64/RISC-V boot image */
 };
 
 /**
@@ -649,6 +650,14 @@ enum image_fmt_t genimg_get_format(const void *img_addr);
 
 int genimg_has_config(struct bootm_headers *images);
 
+/**
+ * booti_is_valid() - Check if an image appears to be an Arm64 image
+ *
+ * @img: Pointer to image
+ * Return: true if the image has the Arm64 magic
+ */
+bool booti_is_valid(const void *img);
+
 /**
  * boot_get_fpga() - Locate the FPGA image
  *