EDAC/cortex: Support big/little configurations of A53 and A57

Calling edac_device_alloc_ctl_info() a second time fails, as the name
has already been registered.

Use the structure in edac_device.h, and register all the cpus up front.
A second call to probe() takes a reference and adds the CPUs described
by the new entry.

Signed-off-by: James Morse <james.morse@arm.com>