clk: add clock driver for MediaTek MT76x8 platform

This patch adds a clock driver for MediaTek MT7628/7688 SoC.
It provides clock gate control as well as getting clock frequency for
CPU/SYS/XTAL and some peripherals.

Signed-off-by: Weijie Gao <weijie.gao@mediatek.com>
diff --git a/drivers/clk/Makefile b/drivers/clk/Makefile
index 8de6777..06131ed 100644
--- a/drivers/clk/Makefile
+++ b/drivers/clk/Makefile
@@ -16,6 +16,7 @@
 obj-y += tegra/
 obj-$(CONFIG_ARCH_ASPEED) += aspeed/
 obj-$(CONFIG_ARCH_MEDIATEK) += mediatek/
+obj-$(CONFIG_ARCH_MTMIPS) += mtmips/
 obj-$(CONFIG_ARCH_MESON) += meson/
 obj-$(CONFIG_ARCH_ROCKCHIP) += rockchip/
 obj-$(CONFIG_ARCH_SOCFPGA) += altera/