meta-ohos-core/README.md: Add Copyright and License for reuse compliance

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

meta-ohos-core/README.md

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+SPDX-FileCopyrightText: Huawei Inc.
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+SPDX-License-Identifier: Apache-2.0
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 This README file contains information about the contents of the meta-ohos-core layer.
 
 Please see the corresponding sections below for details.