Change-Id: I61c9fdfda0c0b3c3ec6249519db23602cf4c2100
Signed-off-by: Dimitris Papastamos <dimitris.papastamos@arm.com>

This patch also fixes the assumption that the counters are disabled on
the resume path.  This is incorrect as the AMU counters are enabled
early in the CPU reset function before `cpuamu_context_restore()`
runs.

Change-Id: I38a94eb166a523f00de18e86860434ffccff2131
Signed-off-by: Dimitris Papastamos <dimitris.papastamos@arm.com>

Change-Id: I504d3f65ca5829bc1f4ebadb764931f8379ee81f
Signed-off-by: Dimitris Papastamos <dimitris.papastamos@arm.com>

The Cortex A75 has 5 AMU counters.  The first three counters are fixed
and the remaining two are programmable.

A new build option is introduced, `ENABLE_AMU`.  When set, the fixed
counters will be enabled for use by lower ELs.  The programmable
counters are currently disabled.

Change-Id: I4bd5208799bb9ed7d2596e8b0bfc87abbbe18740
Signed-off-by: Dimitris Papastamos <dimitris.papastamos@arm.com>

Both Cortex-A75 and Cortex-A55 CPUs use the ARM DynamIQ Shared Unit
(DSU). The power-down and power-up sequences are therefore mostly
managed in hardware, and required software operations are considerably
simpler.

Change-Id: I68b30e6e1ebe7c041d5e67f39c59f08575fc7ecc
Co-authored-by: Sandrine Bailleux <sandrine.bailleux@arm.com>
Signed-off-by: Jeenu Viswambharan <jeenu.viswambharan@arm.com>