[HAL][RCC] Add UNUSED() macro to avoid the generation of a warning related to the unused argument 'Edge'

Src/stm32l1xx_hal_rcc.c

diff --git a/Src/stm32l1xx_hal_rcc.c b/Src/stm32l1xx_hal_rcc.c
index cca9817..76fd8be 100644
--- a/Src/stm32l1xx_hal_rcc.c
+++ b/Src/stm32l1xx_hal_rcc.c
@@ -1009,6 +1009,9 @@
   assert_param(IS_RCC_MCODIV(RCC_MCODiv));
   assert_param(IS_RCC_MCO1SOURCE(RCC_MCOSource));
 
+  /* Prevent unused argument(s) compilation warning */
+  UNUSED(RCC_MCOx);
+
   /* Configure the MCO1 pin in alternate function mode */
   gpio.Mode      = GPIO_MODE_AF_PP;
   gpio.Speed     = GPIO_SPEED_FREQ_HIGH;