MIPS: Netlogic: Reduce size of reset code

MIPS: Netlogic: Reduce size of reset code

Update thread wakeup function to use scratch registers for saving SP and
RA. Move the register restore code needed for thread 0 to the calling
function. This reduces the size of code copied to the reset vector.

Signed-off-by: Jayachandran C <jchandra@broadcom.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/6910/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>