cpmac bugfixes and enhancements

* Resolve some locking issues using atomic_inc/atomic_dec
* move status code in cpmac_check_status
* unmark the BROKEN flag in Kconfig
* move code which should have been in platform code in
  arch/mips/ar7/platform.c
* fixed an IRQ storm which lets the kernel hang
* fixed a double call to netif_start_queue which causes a kernel panic
* don't fail to register the PHY, works on many devices now

Signed-off-by: Matteo Croce <matteo@openwrt.org>
Signed-off-by: Felix Fietkau <nbd@openwrt.org>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>