drivers: serial: nrfx_uarte: Improve UART_NRFX_UARTE_ENHANCED_RX dependency

Enhanced RX cannot be used when UART_x_NRF_HW_ASYNC is used so changing
default value to depends on.

Signed-off-by: Krzysztof Chruściński <krzysztof.chruscinski@nordicsemi.no>

Author: nordic-krch

drivers/serial/Kconfig.nrfx

@@ -60,7 +60,8 @@ config UART_NRFX_UARTE_ENHANCED_RX
 	bool "Enhanced RX handling"
 	depends on UART_ASYNC_API
 	depends on UART_NRFX_UARTE_LEGACY_SHIM
-	default y if !(UART_0_NRF_HW_ASYNC || UART_1_NRF_HW_ASYNC || UART_2_NRF_HW_ASYNC)
+	depends on !(UART_0_NRF_HW_ASYNC || UART_1_NRF_HW_ASYNC || UART_2_NRF_HW_ASYNC)
+	default y
 	help
 	  Enable RX handling mode which is switching buffers on timeout. This is an
 	  enhancement compared to other two modes (default and hardware assisted).