jtag: remove unused function adapter_driver_modules_load()

jtag: remove unused function adapter_driver_modules_load()

Commit c2cecc74b0ac ("Move JTAG interface list to new files.")
merged in mid 2009 introduces an unused and empty function that
the developer expects to use for loading adapter drivers from
shared libraries. This have never happened and the function is
still empty and unused.

Remove it.

Change-Id: I7c88dbf8a9747e96e5ca4e6e7038ac0f232604fd
Signed-off-by: Antonio Borneo <borneo.antonio@gmail.com>
Reviewed-on: http://openocd.zylin.com/5601
Reviewed-by: Andreas Fritiofson <andreas.fritiofson@gmail.com>
Tested-by: jenkins