ARM: OMAP2+: Fix l2dis_3630 for rodata

ARM: OMAP2+: Fix l2dis_3630 for rodata

We don't want to write to .text section. Let's move l2dis_3630
to .data and access it via a pointer.

For calculating the offset, let's optimize out the add and do it
in ldr/str as suggested by Nicolas Pitre <nicolas.pitre@linaro.org>.

Cc: Kees Cook <keescook@chromium.org>
Cc: Laura Abbott <labbott@redhat.com>
Cc: Nishanth Menon <nm@ti.com>
Cc: Richard Woodruff <r-woodruff2@ti.com>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Tero Kristo <t-kristo@ti.com>
Cc: stable@vger.kernel.org # v4.0+
Acked-by: Nicolas Pitre <nico@linaro.org>
Cc: stable@vger.kernel.org # v4.0+
Fixes: 1e6b48116a95 ("ARM: mm: allow non-text sections to be
non-executable")
Signed-off-by: Tony Lindgren <tony@atomide.com>