bcma: add functions to scan cores needed on SoCs

The chip common and mips core have to be setup early in the boot
process to get the cpu clock.
bcma_bus_early_register() gets pointers to some space to store the core
data and searches for the chip common and mips core and initializes
chip common. After that was done and the kernel is out of early boot we
just have to run bcma_bus_register() and it will search for the other
cores, initialize and register them.
The cores are getting the same numbers as before.

Acked-by: Rafał Miłecki <zajec5@gmail.com>
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>
Acked-by: Ralf Baechle <ralf@linux-mips.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>