staging: r8188eu: simplify rtw_make_wlanhdr's error handling

Simplify the error handling in rtw_make_wlanhdr. Exit immediately instead
of jumping to the end of the function. We don't have to do any clean-up.

Signed-off-by: Martin Kaiser <martin@kaiser.cx>
Tested-by: Philipp Hortmann <philipp.g.hortmann@gmail.com> # Edimax N150
Link: https://lore.kernel.org/r/20221230180646.91008-11-martin@kaiser.cx


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