Correct PB_6/PB_7 Serial AF mapping

Author: amitchone

targets/TARGET_STM/TARGET_STM32L0/TARGET_STM32L0x2xZ/TARGET_MTB_MURATA_ABZ/PeripheralPins.c

@@ -104,7 +104,7 @@ const PinMap PinMap_UART_TX[] = {
     {PA_9,       UART_1,   STM_PIN_DATA(STM_MODE_AF_PP, GPIO_PULLUP, GPIO_AF4_USART1)},
     {PA_14,      UART_2,   STM_PIN_DATA(STM_MODE_AF_PP, GPIO_PULLUP, GPIO_AF4_USART2)},
     {PA_14_ALT0, LPUART_1, STM_PIN_DATA(STM_MODE_AF_PP, GPIO_PULLUP, GPIO_AF6_LPUART1)}, // SWCLK
-    {PB_6,       UART_1,   STM_PIN_DATA(STM_MODE_AF_PP, GPIO_PULLUP, GPIO_AF4_USART1)},
+    {PB_6,       UART_1,   STM_PIN_DATA(STM_MODE_AF_PP, GPIO_PULLUP, GPIO_AF0_USART1)},
     {NC,         NC,       0}
 };
 
@@ -114,7 +114,7 @@ const PinMap PinMap_UART_RX[] = {
     {PA_3_ALT0,  LPUART_1, STM_PIN_DATA(STM_MODE_AF_PP, GPIO_PULLUP, GPIO_AF6_LPUART1)},
     {PA_10,      UART_1,   STM_PIN_DATA(STM_MODE_AF_PP, GPIO_PULLUP, GPIO_AF4_USART1)},
     {PA_13,      LPUART_1, STM_PIN_DATA(STM_MODE_AF_PP, GPIO_PULLUP, GPIO_AF6_LPUART1)},  // SWDIO
-    {PB_7,       UART_1,   STM_PIN_DATA(STM_MODE_AF_PP, GPIO_PULLUP, GPIO_AF4_USART1)},
+    {PB_7,       UART_1,   STM_PIN_DATA(STM_MODE_AF_PP, GPIO_PULLUP, GPIO_AF0_USART1)},
     {NC,         NC,       0}
 };