serial: stm32: Increase maximum number of ports

Increase max number of ports for stm32h7
which supports up to 8 uart and usart instances.
Signed-off-by: NGerald Baeza <gerald.baeza@st.com>
Signed-off-by: NBich Hemon <bich.hemon@st.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/stm32-usart.h

@@ -206,7 +206,7 @@ struct stm32_usart_info stm32f7_info = {
 #define USART_ICR_CMCF		BIT(17)		/* F7 */
 
 #define STM32_SERIAL_NAME "ttyS"
-#define STM32_MAX_PORTS 6
+#define STM32_MAX_PORTS 8
 
 #define RX_BUF_L 200		 /* dma rx buffer length     */
 #define RX_BUF_P RX_BUF_L	 /* dma rx buffer period     */