staging: r8188eu: merge rtw_free_hwxmits into its only caller

rtw_free_hwxmits is called only by _rtw_free_xmit_priv. We can merge the
two functions and make the code a bit shorter.

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/20230123205342.229589-24-martin@kaiser.cx


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