When requesting the performance counter overflow interrupt, pass flags
which are compatible with the cevt-r4k driver, in particular
IRQF_SHARED so that the two handlers can share the same IRQ. This is
possible since release 2 of the architecture where there are separate
pending interrupt bits for the timer interrupt and the performance
counter interrupt.

This will be necessary since the FDC interrupt can also be arbitrarily
routed to a CPU interrupt, possibly sharing with the timer, the
performance counters, or both, and it isn't scalable to have all the
handlers able to call other handlers that may be on the same IRQ line.

Shared handlers must also have a unique device pointer so they can be
individually removed, so &mipspmu is now passed in for that instead of
NULL.
Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/9129/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>