staging: r8188eu: Remove rtw_buf_free()

This routine is just a wrapper around kfree(). The wrapper also sets
buffer length to 0, and the pointer to NULL. The length variable is in
the struct to be freed, thus setting it to zero is meaningless. Setting
the pointer to NULL is also not needed.

Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>
Link: https://lore.kernel.org/r/20210805183717.23007-6-Larry.Finger@lwfinger.net


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