staging: r8188eu: remove obsolete defines and comments

Remove some unused phycfg defines and obsolete comments.

Signed-off-by: Martin Kaiser <martin@kaiser.cx>
Link: https://lore.kernel.org/r/20220108124959.313215-6-martin@kaiser.cx


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>