add requests pending/submit count to prevent request queue full
condition by preempting h/w overflow interrupts in software.
We do this due to the delay in the delivery and handling of the
channel overflow error interrupt.
Signed-off-by: Kim Phillips <kim.phillips@freescale.com> Acked-by: Lee Nipper <lee.nipper@freescale.com> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>