timer: starfive: Add Starfive timer support

Add timer driver in Starfive SoC. It is an timer that outside
of CPU core and inside Starfive SoC.

Signed-off-by: Kuan Lim Lee <kuanlim.lee@starfivetech.com>
Reviewed-by: Wei Liang Lim <weiliang.lim@starfivetech.com>
Reviewed-by: Simon Glass <sjg@chromium.org>

drivers/timer/Makefile

@@ -34,3 +34,4 @@ obj-$(CONFIG_MTK_TIMER)		+= mtk_timer.o
 obj-$(CONFIG_MCHP_PIT64B_TIMER)	+= mchp-pit64b-timer.o
 obj-$(CONFIG_IMX_GPT_TIMER)	+= imx-gpt-timer.o
 obj-$(CONFIG_XILINX_TIMER)	+= xilinx-timer.o
+obj-$(CONFIG_STARFIVE_TIMER)	+= starfive-timer.o