scripts: xtensa-build-all: remove imx8/imx8x

To prepare for XTOS deprecation and switch to Zephyr native
drivers on imx8/imx8x, remove the ability to build SOF
with XTOS on them.

Signed-off-by: Laurentiu Mihalcea <laurentiu.mihalcea@nxp.com>

scripts/xtensa-build-all.sh

@@ -8,7 +8,7 @@ set -e
 # Platforms built and tested by default in CI using the `-a` option.
 # They must have a toolchain available in the latest Docker image.
 DEFAULT_PLATFORMS=(
-    imx8 imx8x imx8m imx8ulp
+    imx8m imx8ulp
     rn rmb vangogh
     mt8186 mt8195
 )