[fp16] fp16 cci.20210320

[hardsetting]

Specify library name and version:
fp16/cci.20210320

The version of fp16 added with this PR matches with the default version expected by xnnpack and tensorflow-lite and is newer than the one currently used

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• I've read the guidelines for contributing.
• I've followed the PEP8 style guides for Python code in the recipes.
• I've used the latest Conan client version.
• I've tried at least one configuration locally with the
  conan-center hook activated.

[conan-center-bot]

All green in build 2 (c074a2acde10529e4deb830ee157d93e05c9cb07):

• fp16/cci.20210320@:
  All packages built successfully! (All logs)