The sel argument os nlm_read_c2_status() was not used and the macro
returned the sel 0 in all cases. Fix this by defining two macros:
nlm_read_c2_status0() and nlm_read_c2_status1() to return the two
status registers.

Add functions to write to the status registers as well.
Signed-off-by: Jayachandran C <jchandra@broadcom.com>
Cc: linux-mips@linux-mips.org
Cc: ddaney.cavm@gmail.com
Patchwork: https://patchwork.linux-mips.org/patch/5414/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>