For OProfile to initialise oprofilefs correctly, it needs to know
the number of counters it can represent.

This patch adds a function to the ARM perf-events backend to return
the number of hardware counters available for the current PMU.

Cc: Jamie Iles <jamie.iles@picochip.com>
Signed-off-by: NWill Deacon <will.deacon@arm.com>
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>

The ARM perf-events framework provides support for a number of different
PMUs using struct arm_pmu. The char *name field of this struct can be
used to identify the PMU, but this is cumbersome if used outside of perf.

This patch replaces the name string for a PMU with an enum, which holds
a unique ID for the PMU being represented. This ID can be used to index
an array of names within perf, so no functionality is lost. The presence
of the ID field, allows other kernel subsystems [currently oprofile] to
use their own mappings for the PMU name.

Cc: Jean Pihet <jpihet@mvista.com>
Acked-by: NJamie Iles <jamie.iles@picochip.com>
Signed-off-by: NWill Deacon <will.deacon@arm.com>
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>

The perf events subsystem allows counting of both hardware and
software events. This patch implements the bare minimum for software
performance events.

Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: NJamie Iles <jamie.iles@picochip.com>
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>