mips: lantiq: add support for clk_get_parent()

Provide a simple implementation of clk_get_parent() in the
lantiq subarch so that callers of it will build without errors.

Fixes this build error:
ERROR: modpost: "clk_get_parent" [drivers/iio/adc/ingenic-adc.ko] undefined!

Fixes: 171bb2f ("MIPS: Lantiq: Add initial support for Lantiq SoCs")
Signed-off-by: Randy Dunlap <[email protected]>
Suggested-by: Russell King (Oracle) <[email protected]>
Cc: [email protected]
Cc: John Crispin <[email protected]>
Cc: Thomas Bogendoerfer <[email protected]>
Cc: Jonathan Cameron <[email protected]>
Cc: [email protected]
Cc: Russell King <[email protected]>
Cc: Andy Shevchenko <[email protected]>
Acked-by: Jonathan Cameron <[email protected]>
Acked-by: John Crispin <[email protected]>
Signed-off-by: Thomas Bogendoerfer <[email protected]>

arch/mips/lantiq/clk.c

@@ -158,6 +158,12 @@ void clk_deactivate(struct clk *clk)
 }
 EXPORT_SYMBOL(clk_deactivate);
 
+struct clk *clk_get_parent(struct clk *clk)
+{
+	return NULL;
+}
+EXPORT_SYMBOL(clk_get_parent);
+
 static inline u32 get_counter_resolution(void)
 {
 	u32 res;