clkdev: use clk_hw internally

clk_add_alias() calls clk_get() followed by clk_put() but in between
those two calls it saves away the struct clk pointer to a clk_lookup
structure. This leaves the 'clk' member of the clk_lookup pointing at
freed memory on configurations where CONFIG_COMMON_CLK=y. This is a
problem because clk_get_sys() will eventually try to dereference the
freed pointer by calling __clk_get_hw() on it. Fix this by saving away
the struct clk_hw pointer instead of the struct clk pointer so that when
we try to create a per-user struct clk in clk_get_sys() we don't
dereference a junk pointer.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

include/linux/clkdev.h

@@ -22,6 +22,7 @@ struct clk_lookup {
 	const char		*dev_id;
 	const char		*con_id;
 	struct clk		*clk;
+	struct clk_hw		*clk_hw;
 };
 
 #define CLKDEV_INIT(d, n, c)	\