No functional changes.

Change-Id: I2f28f20944f552447ac4e9e755493cd7c0ea1192
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>

Add some AMU helper functions to allow configuring, reading and
writing of the Group 0 and Group 1 counters.  Documentation for these
helpers will come in a separate patch.

Change-Id: I656e070d2dae830c22414f694aa655341d4e2c40
Signed-off-by: Dimitris Papastamos <dimitris.papastamos@arm.com>