ARM: perf: de-const struct arm_pmu

This patch removes const qualifiers from instances of struct arm_pmu,
and functions initialising them, in preparation for generalising
arm_pmu usage to system (AKA uncore) PMUs.

This will allow for dynamically modifiable structures (locks,
struct pmu) to be added as members of struct arm_pmu.

Acked-by: Jamie Iles <jamie@jamieiles.com>
Reviewed-by: Jean Pihet <j-pihet@ti.com>
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
diff --git a/arch/arm/kernel/perf_event.c b/arch/arm/kernel/perf_event.c
index 53c9c26..7304996 100644
--- a/arch/arm/kernel/perf_event.c
+++ b/arch/arm/kernel/perf_event.c
@@ -90,7 +90,7 @@
 };
 
 /* Set at runtime when we know what CPU type we are. */
-static const struct arm_pmu *armpmu;
+static struct arm_pmu *armpmu;
 
 enum arm_perf_pmu_ids
 armpmu_get_pmu_id(void)