Backport ARMmbed#12052: Fix for ARM issue 11859.

1. Clear UART events before enabling
2. Reset device before return from test case

Author: yarbcy

TESTS/mbed_hal_fpga_ci_test_shield/uart/main.cpp

@@ -133,6 +133,9 @@ static void uart_test_common(int baudrate, int data_bits, SerialParity parity, i
             serial_set_flow_control_direct(&serial, FlowControlRTSCTS, &pinmap);
 #else
             //skip this test case if static pinmap is not supported
+            // Cleanup uart to be able execute next test case
+            serial_free(&serial);
+            tester.reset();
             return;
 #endif
         } else {

targets/TARGET_Cypress/TARGET_PSOC6/psoc6csp/hal/src/cyhal_uart.c

@@ -720,10 +720,12 @@ void cyhal_uart_enable_event(cyhal_uart_t *obj, cyhal_uart_event_t event, uint8_
         obj->irq_cause &= ~event;
         if (event & CYHAL_UART_IRQ_RX_NOT_EMPTY)
         {
+            Cy_SCB_ClearRxInterrupt(obj->base, CY_SCB_RX_INTR_NOT_EMPTY);
             Cy_SCB_SetRxInterruptMask(obj->base, Cy_SCB_GetRxInterruptMask(obj->base) & ~CY_SCB_RX_INTR_NOT_EMPTY);
         }
         if (event & CYHAL_UART_IRQ_TX_EMPTY)
         {
+            Cy_SCB_ClearTxInterrupt(obj->base, CY_SCB_UART_TX_EMPTY);
             Cy_SCB_SetTxInterruptMask(obj->base, Cy_SCB_GetTxInterruptMask(obj->base) & ~CY_SCB_UART_TX_EMPTY);
         }
     }