Added EFA helm chart

[zachdorame]

Issue

N/A

Description of changes

• Added the EFA helm chart from https://github.com/aws-samples/efa-device-plugin-helm
• Added a README.md to the EFA helm chart
• Added a reference to the EFA helm chart in the root README.md

Checklist

• Added/modified documentation as required (such as the README.md for modified charts)
• Incremented the chart version in Chart.yaml for the modified chart(s)
• Manually tested. Describe what testing was done in the testing section below
• Make sure the title of the PR is a good description that can go into the release notes

Testing

ran make verify

Results (only for EFA chart):

Validating chart aws-efa-k8s-device-plugin/ w/ helm v3
WARN - Set to ignore missing schemas
PASS - aws-efa-k8s-device-plugin/templates/daemonset.yaml contains a valid DaemonSet (release-name-aws-efa-k8s-device-plugin)
Validating chart aws-efa-k8s-device-plugin/ w/ helm v2
WARN - Set to ignore missing schemas
PASS - aws-efa-k8s-device-plugin/templates/daemonset.yaml contains a valid DaemonSet (release-name-aws-efa-k8s-device-plugin)

Linting chart aws-efa-k8s-device-plugin/ w/ helm v3
==> Linting /Volumes/workplace/eks-charts/stable/aws-efa-k8s-device-plugin/

1 chart(s) linted, 0 chart(s) failed
Linting chart aws-efa-k8s-device-plugin/ w/ helm v2
==> Linting /Volumes/workplace/eks-charts/stable/aws-efa-k8s-device-plugin/
Lint OK

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.