arm1136: timer: Replace bss variable by gd

Reuse the gd->tbl value for timestamp and add gd->lastinc for lastinc bss
values in the arm1136 timer driver for mx31 and omap24xx

The usage of bss values in drivers before initialisation of bss is forbidden.
In that special case some data in .rel.dyn gets corrupted.

This patch is similiar to the patch Dirk Behme posted
for the armv7/omap-common/timer.c

Tested on the mx31 based qong board

Signed-off-by: Heiko Schocher <hs@denx.de>
cc: Albert ARIBAUD <albert.aribaud@free.fr>
Acked-by: Albert ARIBAUD <albert.aribaud@free.fr>