Rename Smb to SMB

[alexander-ding]

What type of PR is this?

Uncomment only one /kind <> line, hit enter to put that in a new line, and remove leading whitespaces from that line:

/kind api-change
/kind bug
/kind cleanup
/kind design
/kind documentation
/kind failing-test
/kind feature
/kind flake

What this PR does / why we need it:
Improve naming consistency and adhere to Go best practices (using all caps when the name contains acronyms).

Which issue(s) this PR fixes:

Fixes #246

Special notes for your reviewer:
Do not merge before #254 is merged

Does this PR introduce a user-facing change?:

NONE

[k8s-ci-robot]

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This pull-request has been approved by: alexander-ding
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