jtag_add_reset() function

A reset of the TAP state machine can be requested. Whether tms or trst reset is used depends on the capabilities of the target and jtag interface(reset_config command configures this). srst can driver a reset of the TAP state machine and vice versa Application code may need to examine value of jtag_reset_config to determine the proper codepath DANGER! Even though srst drives trst, trst might not be connected to the interface, and it might actually be *harmful* to assert trst in this case. This is why combinations such as "reset_config srst_only srst_pulls_trst" are supported. only req_tlr_or_trst and srst can have a transition for a call as the effects of transitioning both at the "same time" are undefined, but when srst_pulls_trst or vice versa, then trst & srst *must* be asserted together.