clk: at91: Add clock driver

The patch is referred to at91 clock driver of Linux, to make
the clock node descriptions in DT aligned with the Linux's.

Signed-off-by: Wenyou Yang <wenyou.yang@atmel.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/drivers/clk/Kconfig b/drivers/clk/Kconfig
index 6eee8eb..3da63c0 100644
--- a/drivers/clk/Kconfig
+++ b/drivers/clk/Kconfig
@@ -22,5 +22,6 @@
 
 source "drivers/clk/uniphier/Kconfig"
 source "drivers/clk/exynos/Kconfig"
+source "drivers/clk/at91/Kconfig"
 
 endmenu