mtd: onenand: implement cache program feature for 4KiB page onenand

Implement cache program feature for 4KiB page onenand.
This feature improves the write data performance.
The observed 128KiB data program speed change is
from 8827KiB/s to 14156 KiB/s when the feature is enabled.

Signed-off-by: Roman Tereshonkov <roman.tereshonkov@nokia.com>
Acked-by: Mike Frysinger <vapier@gentoo.org>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>