mips32: inline functions in headers must be static

Change-Id: If1d0fc6766cadc2db33408ae5c0968de6b7a1b94
Signed-off-by: Andreas Fritiofson <andreas.fritiofson@gmail.com>
Reviewed-on: http://openocd.zylin.com/4178


Tested-by: jenkins
Reviewed-by: Salvador Arroyo <sarroyofdez@yahoo.es>
Reviewed-by: Stian Skjelstad <stian@nixia.no>