spl: fat: load kernel image before args in falcon

spl: fat: load kernel image before args in falcon

Currently in falcon mode, the FS and raw mmc boot loads the args file
first followed by the kernel image whereas others load in the opposite
order. This inconsistency means falcon boot doesn't behave the same
across various boot media.

For example, in the case where the kernel file is a FIT with the kernel
image present alongside the dtb and the args file is another DT, which
DT should be picked? The one form the FIT or the one set by the args
file? Currently this depends entirely on how the boot media handles
falcon mode.

Therefore, this patch enforces the load order of the kernel image first
followed by the args file in FAT FS boot. So in the above example, the
args file would take precedence.

Reviewed-by: Tom Rini <trini@konsulko.com>
Signed-off-by: Anshul Dalal <anshuld@ti.com>