powerpc/xmon: Add address lookup for percpu symbols

powerpc/xmon: Add address lookup for percpu symbols

Currently, in xmon, there is no obvious way to get an address for a
percpu symbol for a particular cpu. Having such an ability would be
good for debugging the system when percpu variables got involved.

Therefore, this patch introduces a new xmon command "lp" to lookup the
address for percpu symbols. Usage of "lp" is similar to "ls", except
that we could add a cpu number to choose the variable of which cpu we
want to lookup. If no cpu number is given, lookup for current cpu.

Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>