staging: r8188eu: remove rtw_endofpktfile()

The function rtw_endofpktfile() just checks for pkt_len == 0.
Remove rtw_endofpktfile() and merge the check into the caller to
improve readability and simplify the driver code.

Reviewed-by: Philipp Hortmann <philipp.g.hortmann@gmail.com>
Signed-off-by: Michael Straube <straube.linux@gmail.com>
Link: https://lore.kernel.org/r/20220817063223.8140-1-straube.linux@gmail.com


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