[STM32F4xx] bugfix for PR #1707 - more typos

I found and corrected some more typos.

Author: ohagendorf

libraries/mbed/targets/cmsis/TARGET_STM/TARGET_STM32F4/stm32_hal_legacy.h

@@ -1869,12 +1869,12 @@
 #define __USART5_RELEASE_RESET      __HAL_RCC_UART5_RELEASE_RESET
 #define __USART7_CLK_DISABLE        __HAL_RCC_USART7_CLK_DISABLE
 #define __USART7_CLK_ENABLE         __HAL_RCC_USART7_CLK_ENABLE
-#define __USART7_FORCE_RESET        __HAL_RCC_USART7_FORCE_RESET
-#define __USART7_RELEASE_RESET      __HAL_RCC_USART7_RELEASE_RESET
+#define __USART7_FORCE_RESET        __HAL_RCC_UART7_FORCE_RESET
+#define __USART7_RELEASE_RESET      __HAL_RCC_UART7_RELEASE_RESET
 #define __USART8_CLK_DISABLE        __HAL_RCC_USART8_CLK_DISABLE
 #define __USART8_CLK_ENABLE         __HAL_RCC_USART8_CLK_ENABLE
-#define __USART8_FORCE_RESET        __HAL_RCC_USART8_FORCE_RESET
-#define __USART8_RELEASE_RESET      __HAL_RCC_USART8_RELEASE_RESET
+#define __USART8_FORCE_RESET        __HAL_RCC_UART8_FORCE_RESET
+#define __USART8_RELEASE_RESET      __HAL_RCC_UART8_RELEASE_RESET
 #define __USB_CLK_DISABLE         __HAL_RCC_USB_CLK_DISABLE
 #define __USB_CLK_ENABLE          __HAL_RCC_USB_CLK_ENABLE
 #define __USB_FORCE_RESET         __HAL_RCC_USB_FORCE_RESET