feat(fvp): add cpu power control

Most newer CPU's have DSU and CPU power control core-off bit which
means before turning off CPUs from base power controller we need to
turn individual cores off from

feat(fvp): add cpu power control

Most newer CPU's have DSU and CPU power control core-off bit which
means before turning off CPUs from base power controller we need to
turn individual cores off from CPU Power control.

However there are certain older CPU's that don't have DSU and
don't support CPUPWRCTRL_EL1, so populate them as a list
and ignore setting core-off bit for those older CPU's as all newer
CPU's have them.

Note: unfortunately there is no mechanism to identify if a DSU is
present and CPUPWRCTRL_EL1 is supported through any CPU control
registers and CPUPWRCTRL_EL1 is supported only for ARM64 platforms
and not available in ARM32 platforms.

Change-Id: Iba6c3c8db60dbeb177cead7ebc65df8265860da7
Signed-off-by: Govindraj Raja <govindraj.raja@arm.com>

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