ARM: 8537/1: drop unused DEBUG_RODATA from XIP_KERNEL

With CONFIG_DEBUG_RODATA not being sensible under XIP_KERNEL, remove it
from the XIP linker script.

Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>