3. Boot the board into Falcon Mode. SPL will load the kernel and copy
the parameters which are saved in the persistent area to the required address.
+If a valid uImage is not found at the defined location, U-Boot will be
+booted instead.
It is required to implement a custom mechanism to select if SPL loads U-Boot
or another image.
Returns "0" if SPL should start the kernel, "1" if U-Boot
must be started.
+Environment variables
+---------------------
+
+A board may chose to look at the environment for decisions about falcon
+mode. In this case the following variables may be supported:
+
+boot_os : Set to yes/Yes/true/True/1 to enable booting to OS,
+ any other value to fall back to U-Boot (including
+ unset)
+falcon_args_file : Filename to load as the 'args' portion of falcon mode
+ rather than the hard-coded value.
+falcon_image_file : Filename to load as the OS image portion of falcon
+ mode rather than the hard-coded value.
Using spl command
-----------------