serial: 8250_pci: replace switch-case by formula for Intel MID

serial: 8250_pci: replace switch-case by formula for Intel MID

This patch replaces a switch-case by a formula using rational best
approximation that does necessary calculations for intel_mid_set_termios().

Below is a list of the calculations done for all defined baud rates. Each line
in a format: 1) nominator, 2) denominator, 3) prescaler, 4) Fuart, 5) port UART
clock, 6) list of baud rates with DLAB values.

24       25       12 48000000   64000000   4000000(1)
49       50       14 49000000   56000000   3500000(1)
4        5        16 40000000   40000000   2500000(1)
16       25       16 32000000   32000000   500000(4),1000000(2),2000000(1)
24       25       16 48000000   48000000   1500000(2),3000000(1)
2304     3125     16 36864000   36864000   576000(4),1152000(2)
8192     15625    16 26214400   26214400   50(32768),200(8192)
9216     15625    16 29491200   29491200   1800(1024),57600(32),115200(16),
					230400(8),460800(4),921600(2),1843200(1)
12288    15625    16 39321600   39321600   75(32768),150(16384),300(8192),
					600(4096),1200(2048),2400(1024),4800(512),
					9600(256),19200(128),38400(64)
45056    78125    16 28835840   28835840   110(16384)
274432   390625   16 35127296   35127296   134(16384)

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Peter Hurley <peter@hurleysoftware.com>
Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>