rockchip: timer: rockchip_timer: fix compatible and driver name

In the binding for the Rockchip timer the compatible string
consists of a SoC orientated string and a fall back string
"rockchip,rk3288-timer", so remove all unneeded ones and
fix driver name.

Signed-off-by: Johan Jonker <jbx6244@gmail.com>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>