[MTD] OneNAND: Return an error if a read timeout occurs

If OneNAND is operating within specification, all operations should easily be
completed within the 20 millisecond timeout.
This patch faithlessly adds a check for the timeout and returns an error in
that case.

Signed-off-by: Adrian Hunter <ext-adrian.hunter@nokia.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>