[HAL][GENERIC] Update brief of HAL_GetTickFreq()

Src/stm32l1xx_hal.c

diff --git a/Src/stm32l1xx_hal.c b/Src/stm32l1xx_hal.c
index e41fc25..b3ba9c3 100644
--- a/Src/stm32l1xx_hal.c
+++ b/Src/stm32l1xx_hal.c
@@ -355,7 +355,8 @@
 
 /**
   * @brief Return tick frequency.
-  * @retval tick period in Hz
+  * @retval Tick frequency.
+  *         Value of @ref HAL_TickFreqTypeDef.
   */
 uint32_t HAL_GetTickFreq(void)
 {