GitLab

Before suspend the AMU counters should be enabled and after resume
they should be disabled.  Assert that to be consistent with the
AArch64 implementation of `amu_context_{save,restore}()`.

Change-Id: Ia46f77e4062b93afb93721a2890a9b9d2a7f300e
Signed-off-by: Dimitris Papastamos <dimitris.papastamos@arm.com>