ARM: make timer variables in gt_t available for all ARM platforms

All code that attemots to access variables in BSS before relocation
(for example directly or indirectly by board_init_f()) needs to be
fixed. Especially timer.c needs to fix on most of the ARM platforms.

This patch makes timer related variables in gd_t available for
all ARM implementations.

Signed-off-by: Prafulla Wadaskar <prafulla@marvell.com>

Edited commit message.
Signed-off-by: Wolfgang Denk <wd@denx.de>