conf machine: phyimx6.inc replace deprecated SERIAL_CONSOLE
conf machine: phyimx6.inc replace deprecated SERIAL_CONSOLE

from thud SERIAL_CONSOLE is deprecated and replaced by SERIAL_CONSOLES.

Signed-off-by: Jan Remmet <9c9945a0da87ab3eec6bcf12544e291bfd78ecfe@phytec.de>
Signed-off-by: Stefan Müller-Klieser <a3e08e35e4a42be768e7d0e76ae1ba321c2a66dd@phytec.de>

PHYTEC-Messtechnik-GmbH/meta-phytec,PHYTEC-Messtechnik-GmbH/meta-phytec,PHYTEC-Messtechnik-GmbH/meta-phytec,PHYTEC-Messtechnik-GmbH/meta-phytec,PHYTEC-Messtechnik-GmbH/meta-phytec