MIPS: Tracing: Cleanup of instructions used

This patch adds some cleanups of the instructions:
  o use macros instead of magic numbers
  o use macros instead of variables to reduce some overhead
  o add new macro for the jal instruction

Signed-off-by: Wu Zhangjin <wuzhangjin@gmail.com>
Cc: linux-mips <linux-mips@linux-mips.org>
Cc: David Daney <david.s.daney@gmail.com>
Patchwork: http://patchwork.linux-mips.org/patch/1229/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>