target/icepick.cfg: Add support for Test TAPs in ICEPick C

target/icepick.cfg: Add support for Test TAPs in ICEPick C

In addition to the debug TAPs, the ICEPick C also supports
a bank of Test TAPs (limited functionality intended for
non-debuggable targets). Added support for Test TAPs to
the icepick_c_tapenable routine. Port numbers of 0 to 15
will continue to be handled as a debug TAP number. Test
TAPs will be port numbers of 16 to 31.

This functionality will be needed for doing a flash
mass erase on CC26xx/CC13xx targets. It is possible
for user application to block even adding the Cortex M
TAP to the scan chain, so the only way to unbrick the
target and erase the flash is using a component on a
test TAP of the device's ICEPick router.

Change-Id: I0aa52a08d43a00cbd396efdeadd504fc31c98510
Signed-off-by: Edward Fewell <efewell@ti.com>
Reviewed-on: http://openocd.zylin.com/5715
Tested-by: jenkins
Reviewed-by: Antonio Borneo <borneo.antonio@gmail.com>