ARM: 8703/1: debug.S: move hexbuf to a writable section

This was located in .text which is meant to be read-only. And in the XIP
case this shortcut simply doesn't work and may trigger a Flash controller
mode switch and crash the kernel. Move it to the .bss area.

Signed-off-by: Nicolas Pitre <nico@linaro.org>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>