Update controller-gen handling in Makefile

[ashwani2k]

What this PR does / why we need it: Makefile used in this project has certain gaps which creeps in when generating CRDs via make manifests namely -

• It doesn't allow configuring a required controller-gen version
• It still uses go get instead of go install while installing controller-gen
• It only checks if the controller-gen exists and doesn't check if the version installed is what is specified as the required version for generation.

This PR fixes this by enhancing the Makefile to handle these limitations or gaps.

Which issue(s) this PR fixes: Fixes #

Special notes for your reviewer:

Release note:

A bug in Makefile handling of `controller-gen` version and its installation is now fixed'