drivers serial nrfx: Speed up for simulation

Increase the busy wait time granularity while runing in simulation
for poll mode. In this mode, the driver spends a *lot* of time
waiting for the UART to be done. The smallest frame time is
~10µs @ 1Mbps, so busywaiting in very small increments
is very wastefull as we keep shuting down and turning on the simulated
MCU.
Let's increase the busy wait time increments of the driver to 3 micros,
which should not change much the behaviour.

Signed-off-by: Alberto Escolar Piedras <[email protected]>

Author: aescolar

drivers/serial/uart_nrfx_uarte.c

@@ -484,7 +484,11 @@ static int wait_tx_ready(const struct device *dev)
 		/* wait arbitrary time before back off. */
 		bool res;
 
+#if defined(CONFIG_ARCH_POSIX)
+		NRFX_WAIT_FOR(is_tx_ready(dev), 33, 3, res);
+#else
 		NRFX_WAIT_FOR(is_tx_ready(dev), 100, 1, res);
+#endif
 
 		if (res) {
 			key = irq_lock();
@@ -1502,7 +1506,7 @@ static void uarte_nrfx_poll_out(const struct device *dev, unsigned char c)
 			}
 
 			irq_unlock(key);
-			Z_SPIN_DELAY(2);
+			Z_SPIN_DELAY(3);
 		}
 	} else {
 		key = wait_tx_ready(dev);