staging: r8188eu: replace hand coded loop with list_for_each_entry

In function rtw_get_stainfo, we can use list_for_each_entry to iterate
over the list of stations and make the code a bit simpler.

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/20230211170223.419205-1-martin@kaiser.cx


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