fpga_ci_test_shield-uart: Disable test cases not supported on NRF52840_DK target

According to the documentation, `NRF52840_DK` does not support odd parity and 2 stop bits. Skip these test case using #if !defined(TARGET_NRF52840) directive.
This is temporary solution. In the future we shell consider adding `uart_get_capabilities()` function.
-

Author: mprse

TESTS/mbed_hal_fpga_ci_test_shield/uart/main.cpp

@@ -338,7 +338,9 @@ Case cases[] = {
     Case("38400, 8N1, FC off", one_peripheral<UARTNoFCPort, DefaultFormFactor, fpga_uart_test_common_no_fc<38400, 8, ParityNone, 1, false> >),
     Case("115200, 8N1, FC off", one_peripheral<UARTNoFCPort, DefaultFormFactor, fpga_uart_test_common_no_fc<115200, 8, ParityNone, 1, false> >),
     // stop bits
+#if !defined(TARGET_NRF52840)
     Case("9600, 8N2, FC off", one_peripheral<UARTNoFCPort, DefaultFormFactor, fpga_uart_test_common_no_fc<9600, 8, ParityNone, 2, false> >),
+#endif
 
 #if DEVICE_SERIAL_FC
     // Every set of pins from every peripheral.
@@ -355,11 +357,16 @@ Case cases[] = {
     Case("115200, 8N1, FC on", one_peripheral<UARTPort, DefaultFormFactor, fpga_uart_test_common<115200, 8, ParityNone, 1, false> >),
     // data bits: not tested (some platforms support 8 bits only)
     // parity
+#if !defined(TARGET_NRF52840)
     Case("9600, 8O1, FC on", one_peripheral<UARTPort, DefaultFormFactor, fpga_uart_test_common<9600, 8, ParityOdd, 1, false> >),
+#endif
     Case("9600, 8E1, FC on", one_peripheral<UARTPort, DefaultFormFactor, fpga_uart_test_common<9600, 8, ParityEven, 1, false> >),
     // stop bits
+#if !defined(TARGET_NRF52840)
     Case("9600, 8N2, FC on", one_peripheral<UARTPort, DefaultFormFactor, fpga_uart_test_common<9600, 8, ParityNone, 2, false> >),
 #endif
+#endif
+
 };
 
 utest::v1::status_t greentea_test_setup(const size_t number_of_cases)