serial: 8250_dw: Revert: Do not reclock if already at correct rate

Commit e5d6bd2 ("serial: 8250_dw: Do not reclock if already at
correct rate") breaks the dw UARTs on Intel Bay Trail (BYT) and
Cherry Trail (CHT) SoCs.

Before this change the RTL8732BS Bluetooth HCI which is found
connected over the dw UART on both BYT and CHT boards works properly:

Bluetooth: hci0: RTL: examining hci_ver=06 hci_rev=000b lmp_ver=06 lmp_subver=8723
Bluetooth: hci0: RTL: rom_version status=0 version=1
Bluetooth: hci0: RTL: loading rtl_bt/rtl8723bs_fw.bin
Bluetooth: hci0: RTL: loading rtl_bt/rtl8723bs_config-OBDA8723.bin
Bluetooth: hci0: RTL: cfg_sz 64, total sz 24508
Bluetooth: hci0: RTL: fw version 0x365d462e

where as after this change probing it fails:

Bluetooth: hci0: RTL: examining hci_ver=06 hci_rev=000b lmp_ver=06 lmp_subver=8723
Bluetooth: hci0: RTL: rom_version status=0 version=1
Bluetooth: hci0: RTL: loading rtl_bt/rtl8723bs_fw.bin
Bluetooth: hci0: RTL: loading rtl_bt/rtl8723bs_config-OBDA8723.bin
Bluetooth: hci0: RTL: cfg_sz 64, total sz 24508
Bluetooth: hci0: command 0xfc20 tx timeout
Bluetooth: hci0: RTL: download fw command failed (-110)

Revert the changes to fix this regression.

Fixes: e5d6bd2 ("serial: 8250_dw: Do not reclock if already at correct rate")
Cc: stable@vger.kernel.org
Cc: Peter Collingbourne <pcc@google.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Peter Collingbourne <pcc@google.com>
Link: https://lore.kernel.org/r/20240317214123.34482-1-hdegoede@redhat.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: jwrdegoede

drivers/tty/serial/8250/8250_dw.c

@@ -356,18 +356,18 @@ static void dw8250_set_termios(struct uart_port *p, struct ktermios *termios,
 	long rate;
 	int ret;
 
+	clk_disable_unprepare(d->clk);
 	rate = clk_round_rate(d->clk, newrate);
-	if (rate > 0 && p->uartclk != rate) {
-		clk_disable_unprepare(d->clk);
+	if (rate > 0) {
 		/*
 		 * Note that any clock-notifer worker will block in
 		 * serial8250_update_uartclk() until we are done.
 		 */
 		ret = clk_set_rate(d->clk, newrate);
 		if (!ret)
 			p->uartclk = rate;
-		clk_prepare_enable(d->clk);
 	}
+	clk_prepare_enable(d->clk);
 
 	dw8250_do_set_termios(p, termios, old);
 }