KVM: arm64: nv: Reload PMU events upon MDCR_EL2.HPME change

MDCR_EL2.HPME is the 'global' enable bit for event counters reserved for
EL2. Give the PMU a kick when it's changed to ensure events are
reprogrammed before returning to the guest.

Reviewed-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20241217175550.3658212-1-oliver.upton@linux.dev


Signed-off-by: Oliver Upton <oliver.upton@linux.dev>