deadline-iosched.c: we were already doing single batches so it makes (cont)

sense to me to reduce the read/write submit times. OMAP4460 runs with 128HZ so read submits occur 4 times every kernel tick and write submits occur 1 time per kernel tick (was 1 submit every 5 ticks before). This seems to have improved latency according to tests.

Signed-off-by: franciscofranco <franciscofranco.1990@gmail.com>