Original code would incorrectly bypass serialization if the DPC
thread were performing a big-hammer operation (ISP abort). This
short circuit, though rare, would subsequently stomp on a
secondary thread's mailbox command execution. Found during
ISP81XX testing.
Signed-off-by: Andrew Vasquez <andrew.vasquez@qlogic.com> Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>