arm: Use common cpu_topology structure and functions.

Currently, ARM32 and ARM64 uses different data structures to represent
their cpu topologies. Since, we are moving the ARM64 topology to common
code to be used by other architectures, we can reuse that for ARM32 as
well.

Take this opprtunity to remove the redundant functions from ARM32 and
reuse the common code instead.

To: Russell King <linux@armlinux.org.uk>
Signed-off-by: Atish Patra <atish.patra@wdc.com>
Tested-by: Sudeep Holla <sudeep.holla@arm.com> (on TC2)
Reviewed-by: Sudeep Holla <sudeep.holla@arm.com>
Signed-off-by: Paul Walmsley <paul.walmsley@sifive.com>