realtek: Reduce variable scopes

realtek: Reduce variable scopes

Linus prefers to have loop initializers nice and tightly scoped. In
OpenWRT this has been possible since 41a1a652fbd4 ("kernel: backport
gnu11 upgrade").

This patch cleans up variable scope while trying to do the above for
'simple for loops'.

This cleans up and simplifies some functions and code, and pulls in
variables to a smaller scope.

Signed-off-by: Olliver Schinagl <oliver@schinagl.nl>