[PATCH] ahci: ignore PORT_IRQ_IF_ERR on JMB controllers

JMicron AHCI controllers set PORT_IRQ_IF_ERR on device errors.  The
IRQ status bit indicates interface error or protocol mismatch and ahci
driver interprets it into AC_ERR_ATA_BUS.  So, whenever an ATAPI
device raises check condition, ahci interprets it as ATA bus error and
thus resets it which, in turn, raises check condition thus creating a
reset loop and rendering the device unuseable.

This patch makes JMB controllers ignore PORT_IRQ_IF_ERR when
interpreting error condition.

Signed-off-by: Tejun Heo <htejun@gmail.com>
Cc: Justin Tsai <justin@jmicron.com>