m5: Expose m5 pseudo-instructions to C/C++ via a static library

m5: Expose m5 pseudo-instructions to C/C++ via a static library

Updated the util/m5/Makefile.arm so that m5op_arm.S is used to create
a static library - libm5.a. Allowing users to insert m5
psuedo-instructions into their applications for fine-grained
checkpointing, switching cpus or dumping statistics. e.g.

#include <m5op.h>

void foo(){
	...
	m5_reset_stats(<delay>,<period>)
	m5_work_begin(<workid>,<threadid>);
	...
	m5_work_end(<workid>,<threadid>);
	m5_dump_stats(<delay>,<period>);
}