SPL: make struct spl_image 64-bit safe

Since entry_point and load_addr are addresses, they should be
represented as longs to cover the whole address space and to avoid
warning when compiling the SPL in 64-bit.
Also adjust debug prints to add the 'l' specifier, where needed.

Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Reviewed-by: Alexander Graf <agraf@suse.de>
Reviewed-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Tom Rini <trini@konsulko.com>
Acked-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Reviewed-by: Jagan Teki <jagan@openedev.com>