Correct the name of the structure used for TCP socket options.

The structure was renamed while refactoring Netflix's KTLS changes for
upstreaming, but the original name remained in tcp.4 and was
subsequently copied to ktls.4.

PR: 254141
Reported by: asomers
Approved by: re (gjb)

(cherry picked from commit c5a365623f88999b524d94003187ef09fda55f67)
(cherry picked from commit 0fc5395122b4b50564f3dc9164830a0d1635b622)