Blackfin arch: fix bug - sometimes there is no response to the hitting key in...

Blackfin arch: fix bug - sometimes there is no response to the hitting key in uboot for bf561-ezkit when running with 50mhz SCLK

use 10 delays rather than 7

Signed-off-by: Mike Frysinger <vapier.adi@gmail.com>
Signed-off-by: Bryan Wu <cooloney@kernel.org>