IB/ipath: Remove unsafe fastrcvint code from interrupt handler

The fastrcvint code's purpose was to avoid reading the interrupt
status if kernel packets were in the receive queue (to reduce
overhead).  Because intstatus was not read, we could miss the error
interrupt bit indicating freeze mode, since it only delivers a single
interrupt, even if still pending after intclear is written.

This patch removes that unsafe optimization.

Signed-off-by: Dave Olson <dave.olson@qlogic.com>
Signed-off-by: Roland Dreier <rolandd@cisco.com>