MIPS: Netlogic: SMP wakeup code update

Update for core intialization code.  Initialize status register
after receiving NMI for CPU wakeup. Add the low level L1D flush
code before enabling threads in core.

Also convert the ehb to _ehb so that it works under more GCC
versions.

Signed-off-by: Jayachandran C <jayachandranc@netlogicmicro.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/3755/
Patchwork: https://patchwork.linux-mips.org/patch/4095/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>