S5P: timer: replace bss variable by gd

Use the global data instead of bss variable, replace as follow.

count_value -> removed
timestamp -> tbl
lastdec -> lastinc

Signed-off-by: Minkyu Kang <mk7.kang@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Acked-by: Albert ARIBAUD <albert.aribaud@free.fr>