Revert "MIPS: BCM63XX: Call board_register_device from device_initcall()"

This commit causes a race between PCI scan and SSB fallback SPROM handler
registration, causing the wifi to not work on slower systems. The only
subsystem touched from board_register_devices is platform device
registration, which is safe as an arch init call.

This reverts commit d64ed7ad

 [MIPS:
BCM63XX: Call board_register_device from device_initcall()].

Signed-off-by: Jonas Gorski <jogo@openwrt.org>
To: linux-mips@linux-mips.org
Cc: John Crispin <blogic@openwrt.org>
Cc: Maxime Bizon <mbizon@freebox.fr>
Cc: Florian Fainelli <florian@openwrt.org>
Cc: Kevin Cernekee <cernekee@gmail.com>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>