IB/ehca: Replace get_paca()->paca_index by the more portable raw_smp_processor_id()

We can use raw_smp_processor_id() here because the processor ID is
only used for debug output and therefore our use is preemption-unsafe.

Signed-off-by: Joachim Fenkes <fenkes@de.ibm.com>
Signed-off-by: Roland Dreier <rolandd@cisco.com>