[ARM] omap: allow double-registering of clocks

This stops things blowing up if a 'struct clk' to be passed more
than once to clk_register(), which will be required when we decouple
struct clk's from their names.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
diff --git a/arch/arm/plat-omap/clock.c b/arch/arm/plat-omap/clock.c
index df58f5d..6b3ef2a 100644
--- a/arch/arm/plat-omap/clock.c
+++ b/arch/arm/plat-omap/clock.c
@@ -292,6 +292,12 @@
 	if (clk == NULL || IS_ERR(clk))
 		return -EINVAL;
 
+	/*
+	 * trap out already registered clocks
+	 */
+	if (clk->node.next || clk->node.prev)
+		return 0;
+
 	mutex_lock(&clocks_mutex);
 	list_add(&clk->node, &clocks);
 	if (clk->init)