ARM: dts: imx6sx-sabreauto: add flexcan support

The CAN transceiver on MX6SX Sabreauto board seems in sleep mode by default
after power up the board. User has to press the wakeup key on ARD baseboard
before using the transceiver, or it may not work properly when power up the
board at the first time(warm reset does not have such issue).

This patch operates the wake pin too besides stby/en pins by chaining them
together in regulator mode.

Signed-off-by: Aisheng Dong <aisheng.dong@nxp.com>
Signed-off-by: Joakim Zhang <qiangqing.zhang@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>