staging: r8188eu: remove odm ext lna info

The ext lna info is never set. Remove it and fix up the one place
where it's read.

Signed-off-by: Martin Kaiser <martin@kaiser.cx>
Link: https://lore.kernel.org/r/20211010175204.24029-11-martin@kaiser.cx


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