LF-3494: arch: arm64: imx8mp-evk-sof-wm8960: remove useless routes

LF-3494: arch: arm64: imx8mp-evk-sof-wm8960: remove useless routes

Both SAI3.IN and SAI3.OUT related routes are added automatically
on topology load, so there is no need to specify these routes in
DTS. On the other hand not all topologies have both SAI3 IN and
OUT ports - like KWD topology for instance which has just SAI3.IN.

Signed-off-by: Viorel Suman <viorel.suman@nxp.com>
Reviewed-by: Daniel Baluta <daniel.baluta@nxp.com>
(cherry picked from commit 1dda13ef4d141da0ac32b38ac25729e28f7ad491)