wil6210: use INTX interrupt by default

Currently there is a problem with MSI interrupts and
suspend/resume which causes FW crashes. The problem
is under investigation but for now switch to using
INTX interrupts by default until it is resolved.

Change-Id: Ic2ec8ff2173b82efdd3daa114bb2336285d386f3
Signed-off-by: Lior David <liord@codeaurora.org>