The name "serial_ns16550" is not handy because the devices
will have the names like "serial_ns165500", "serial_ns165501",
"serial_ns165502" etc.

The names like "ns16550_serial0" and "ns16550_serial1" look
much better.

Also it is reasonable to make serial driver's names unification.
E.g. see the names for drivers in drivers/serial directory:
 "netx_serial",
 "mpc5xxx_serial",
 "altera_serial",
 "s3c_serial",
 "imx_serial",
 "pxa_serial",
 "blackfin_serial",
 "stm_serial",
 "pl010_serial",
and even "g_serial" in ./drivers/usb/gadget/serial.c

Signed-off-by: Antony Pavlov <antonynpavlov@gmail.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>