linux-intel: Remove config fix for CONFIG_SERIAL_OF_PLATFORM warning

This used to throw a warning. We can now drop it as upstream fixed it so
it is not enabled anymore.

Signed-off-by: Andrei Gherzan <andrei.gherzan@huawei.com>

meta-oniro-staging/dynamic-layers/meta-intel/recipes-kernel/linux/linux-intel_5.10.bbappend

-# SPDX-FileCopyrightText: Huawei Inc.
-#
-# SPDX-License-Identifier: Apache-2.0
-
-FILESEXTRAPATHS_prepend := "${THISDIR}/linux:"
-
-SRC_URI += "file://misc.cfg"

meta-oniro-staging/dynamic-layers/meta-intel/recipes-kernel/linux/linux/misc.cfg

-# SPDX-FileCopyrightText: Huawei Inc.
-#
-# SPDX-License-Identifier: Apache-2.0
-
-# Avoid kernel build warnings for x86 nonexitent config
-CONFIG_SERIAL_OF_PLATFORM=n