rockchip: rk3036: use rockchip_stimer_init from spl_common.o

rockchip: rk3036: use rockchip_stimer_init from spl_common.o

The only difference with the implementation in spl_common.c is that we
check whether the timer has already been enabled. Considering this is
running in SPL, the first stage on RK3036, I feel like it's guaranteed
to not be enabled by default. No public TRM though and I don't have
access to an RK3036 device so take this as a guess.

Size of SPL binary increases by 8B for evb-rk3036.

Signed-off-by: Quentin Schulz <quentin.schulz@cherry.de>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>