SPL: Rework how we inform about un-headered images

SPL: Rework how we inform about un-headered images

First, remove the puts from the case where we don't have an mkimage
header as this is somewhat common and intentional for no-arg target
images.  Second, rework the final switch statement in board_init_r to,
in the case of !CONFIG_SPL_OS_BOOT be only about doing debug prints
about if we know what the magic is or not (the CONFIG_SPL_OS_BOOT case
is unchanged).  Then we call jump_to_image_no_args().  This gives us the
same behavior as before but with slightly smaller code.

Signed-off-by: Tom Rini <trini@ti.com>