To allow booting Linux on a CPU with physical ID != 0, we need to
provide a mapping from the logical CPU number to the physical CPU
number.

This patch adds such a mapping and populates it during boot.
Signed-off-by: NWill Deacon <will.deacon@arm.com>
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>