staging: r8188eu: simplify rtl8188eu_xmit_tasklet

Simplify the rtl8188eu_xmit_tasklet function. Remove an unnecessary
temporary variable and reformat the code.

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/20221230180646.91008-7-martin@kaiser.cx


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