refactor(st-clock): remove unused struct

The struct clk_fixed_rate is used nowhere in the code, remove its
definition.

Change-Id: I139ad05a249357da96a996feabd4b1f53e290f2a
Signed-off-by: Yann Gautier <yann.gautier@foss.st.com>
diff --git a/drivers/st/clk/clk-stm32-core.h b/drivers/st/clk/clk-stm32-core.h
index 3815d7c..bfb5f11 100644
--- a/drivers/st/clk/clk-stm32-core.h
+++ b/drivers/st/clk/clk-stm32-core.h
@@ -108,11 +108,6 @@
 
 };
 
-struct clk_fixed_rate {
-	const char *name;
-	unsigned long fixed_rate;
-};
-
 struct clk_gate_cfg {
 	uint32_t offset;
 	uint8_t bit_idx;