[MIPS] Split the micro-assembler from tlbex.c.

This patch moves the micro-assembler in a separate implementation, as
it is useful for further run-time optimizations. The only change in
behaviour is cutting down printk noise at kernel startup time.

Checkpatch complains about macro parameters which aren't protected by
parentheses. I believe this is a flaw in checkpatch, the paste operator
used in those macros won't work with parenthesised parameters.

Signed-off-by: Thiemo Seufer <ths@networkno.de>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>