move booti_setup to arch/arm/lig/image.c

Follow bootz's pattern by moving the booti_setup to arch/arm/lib.
This allows to use booti_setup in other paths, e.g booting
an Android image containing Image format.

Note that kernel relocation is move out of booti_setup and it is the
caller's responsibility to do it and allows them do it differently. say,
cmd/booti.c just do a manually, while in the bootm path, we can use
bootm_load_os(with some changes).

Signed-off-by: Bin Chen <bin.chen@linaro.org>
Reviewed-by: Tom Rini <trini@konsulko.com>