Bit 7 of UCR3 is described in the i.MX reference manuals (with the exception
of i.MX1) as follows:

ADNIMP: Autobaud Detection Not Improved-. Disables new features of
	autobaud detection (See Baud Rate Automatic Detection
	Protocol, for more details).

	0 Autobaud detection new features selected
	1 Keep old autobaud detection mechanism

The "new features" mechanism occasionally causes the receiver to get out of sync
and continuously produces received characters of '0xff'.

In order to reproduce the problem:

$ cs0.baudrate=19200
- Change the terminal baudrate to 19200
- Type in the console and it should look good
- Change the terminal baudrate back to 115200
- Type 'b' in the console, then a stream of '0xff' is transmitted in loop

Setting the ADNIMP bit avoids the transmission of '0xff' in loop.

Also rename the bit definition as per the reference manual.

Tested on mx6q.

Based on a patch from Eric Nelson for U-boot.

Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>