tty: 8250: Add note for PX-835

The PX-835 and PX-846 are variants of each other, clarify that
in the comment for the card.
This patch makes no functional difference.

Signed-off-by: Cameron Williams <cang1@live.co.uk>
Link: https://lore.kernel.org/r/DU0PR02MB78998840C2EBED91AABD4494C4DBA@DU0PR02MB7899.eurprd02.prod.outlook.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: Cameron Williams

drivers/tty/serial/8250/8250_pci.c

@@ -5493,7 +5493,7 @@ static const struct pci_device_id serial_pci_tbl[] = {
 		0, 0,
 		pbn_oxsemi_4_15625000 },
 	/*
-	 * Brainboxes PX-846
+	 * Brainboxes PX-835/PX-846
 	 */
 	{	PCI_VENDOR_ID_INTASHIELD, 0x4008,
 		PCI_ANY_ID, PCI_ANY_ID,