[nrf fromtree] drivers: uart: nrf: rx_timeout_slab incorrectly set

When rx_timeout is set to a sufficiently small value,
rx_timeout_slab could potentially get set to a greater
than necessary value that causes spurious UART_RX_RDY
events.

Fixes #62828

Signed-off-by: Jacob Preston <[email protected]>
(cherry picked from commit 52c5517)

Author: pres2300

drivers/serial/uart_nrfx_uarte.c

@@ -844,15 +844,7 @@ static int uarte_nrfx_rx_enable(const struct device *dev, uint8_t *buf,
 	}
 
 	data->async->rx_timeout = timeout;
-	/* Set minimum interval to 3 RTC ticks. 3 is used due to RTC limitation
-	 * which cannot set timeout for next tick. Assuming delay in processing
-	 * 3 instead of 2 is used. Note that lower value would work in a similar
-	 * way but timeouts would always occur later than expected,  most likely
-	 * after ~3 ticks.
-	 */
-	data->async->rx_timeout_slab =
-		MAX(timeout / RX_TIMEOUT_DIV,
-		    NRFX_CEIL_DIV(3 * 1000000, CONFIG_SYS_CLOCK_TICKS_PER_SEC));
+	data->async->rx_timeout_slab = timeout / RX_TIMEOUT_DIV;
 
 	data->async->rx_buf = buf;
 	data->async->rx_buf_len = len;