clk: consoldiate the __clk_get_hw() declarations

Without this we were getting errors like:

In file included from drivers/clk/clkdev.c:22:0:
drivers/clk/clk.h:36:23: error: static declaration of '__clk_get_hw' follows non-static declaration
include/linux/clk-provider.h:808:16: note: previous declaration of '__clk_get_hw' was here

Fixes: 59fcdce425 ("clk: Remove ifdef for COMMON_CLK in clk-provider.h")
fixes: 73e0e496af ("clkdev: Always allocate a struct clk and call __clk_get() w/ CCF")
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>

drivers/clk/imx/clk-imx6ul.c

@@ -12,6 +12,7 @@
 #include <dt-bindings/clock/imx6ul-clock.h>
 #include <linux/clk.h>
 #include <linux/clkdev.h>
+#include <linux/clk-provider.h>
 #include <linux/err.h>
 #include <linux/init.h>
 #include <linux/io.h>