Pull-ups for SAM9 UART/USART TX lines were disabled in a previous
commit. However, several chips in the SAM9 family require pull-ups to
prevent the TX lines from falling (and causing an endless break
condition) when the transceiver is disabled.

From the SAM9G20 datasheet, 32.5.1: "To prevent the TXD line from
falling when the USART is disabled, the use of an internal pull up
is mandatory.". This commit reenables the pull-ups for all chips having
that sentence in their datasheets.

Fixes: 5e04822f ("ARM: dts: at91: fixes uart pinctrl, set pullup on rx, clear pullup on tx")
Signed-off-by: Ingo van Lil <inguin@gmx.de>
Cc: Peter Rosin <peda@axentia.se>
Link: https://lore.kernel.org/r/20191203142147.875227-1-inguin@gmx.deSigned-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>