83xx NAND boot: wait for LTESR[CC]

At least some revisions of the 8313, and possibly other chips, do not
wait for all pages of the initial 4K NAND region to be loaded before
beginning execution; thus, we wait for it before branching out of the
first NAND page.

This fixes warm reset problems when booting from NAND on 8313erdb.

Signed-off-by: Scott Wood <scottwood@freescale.com>
Acked-by: Kim Phillips <kim.phillips@freescale.com>