x86/IO-APIC: clear remoteIRR in clear_IO_APIC_pin()

x86/IO-APIC: clear remoteIRR in clear_IO_APIC_pin()

It was found that in a crash scenario, the remoteIRR bit in an IO-APIC
RTE could be left set, causing problems when bringing up a kdump
kernel. While this generally is most important to be taken care of in
the new kernel (which usually would be a native one), it still seems
desirable to also address this problem in Xen so that (a) the problem
doesn't bite Xen when used as a secondary emergency kernel and (b) an
attempt is being made to save un-fixed secondary kernels from running
into said problem.

Based on a Linux patch from suresh.b.siddha@intel.com.

Signed-off-by: Jan Beulich <jbeulich@novell.com>