linux-phytec-ti

tile: define a macro ktext_writable_addr to get writable kernel text address

It is used by kgdb, ftrace, kprobe and jump label, so we factor
this out into a helper routine.

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