tile/jump_label: add jump label support for TILE-Gx

Add the arch-specific code to support jump label for TILE-Gx. This
code shares NOP instruction with ftrace, so we move it to a common
header file.

Reviewed-by: Chris Metcalf <cmetcalf@ezchip.com>
Signed-off-by: Zhigang Lu <zlu@ezchip.com>
Signed-off-by: Chris Metcalf <cmetcalf@ezchip.com>