[MTD] OneNAND: release CPU in cycles

This patch teaches OneNAND to release processor in
read/write/erase cycles and let other processes proceed.
Also, remove buggi touch watchdog call which only hides
the problem instead of solving it.

Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>