Move the C-code after all macros:  A follow-on patch which
introduces helpers to access the SYS_* registers needs this to build.

Just code shuffling, no functional changes.
Signed-off-by: Manuel Lauss <manuel.lauss@gmail.com>
Cc: Linux-MIPS <linux-mips@linux-mips.org>
Patchwork: https://patchwork.linux-mips.org/patch/7461/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>