fix(st-clock): correct MISRA C2012 15.6

Add braces to correct MISRA C2012 15.6 warning:
The body of an iteration-statement or a selection-statement shall be a
compound-statement.

Signed-off-by: Yann Gautier <yann.gautier@st.com>
Change-Id: If26f3732d31df11bf389a16298ec9e9d8a4a2279
diff --git a/drivers/st/clk/clk-stm32-core.c b/drivers/st/clk/clk-stm32-core.c
index 28e9878..8584a52 100644
--- a/drivers/st/clk/clk-stm32-core.c
+++ b/drivers/st/clk/clk-stm32-core.c
@@ -838,8 +838,9 @@
 		}
 	}
 
-	if ((mmio_read_32(address) & mask_rdy) != mask_test)
+	if ((mmio_read_32(address) & mask_rdy) != mask_test) {
 		return -ETIMEDOUT;
+	}
 
 	return 0;
 }