Reduce OneNAND IPL common code

OneNAND IPL has common codes for RAM init, load data, and jump to 2nd
bootloader, but it's common code used about 300~400 bytes. So board
specific codes, such as lowlevel_init, can't has enough code. It make
a difficult to implement OneNAND IPL.

his patch make this common code as small as possible. and give
lowlevel_init can have more codes.

Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Scott Wood <scottwood@freescale.com>