perf: Fix task context PMU for Hetero

On HETEROGENEOUS hardware (ARM big.Little, Intel Alderlake etc.) each
CPU might have a different hardware PMU. Since each such PMU is
represented by a different struct pmu, but we only have a single HW
task context.

That means that the task context needs to switch PMU type when it
switches CPUs.

Not doing this means that ctx->pmu calls (pmu_{dis,en}able(),
{start,commit,cancel}_txn() etc.) are called against the wrong PMU and
things will go wobbly.

Fixes: f83d2f91 ("perf/x86/intel: Add Alder Lake Hybrid support")
Reported-by: Kan Liang <kan.liang@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Kan Liang <kan.liang@linux.intel.com>
Link: https://lkml.kernel.org/r/YMsy7BuGT8nBTspT@hirez.programming.kicks-ass.net