staging: rtl8723au: core: rtw_xmit: Add blank line after declarations

The following patch fixes the checkpatch.pl warning:

drivers/staging/rtl8723au/core/rtw_xmit.c WARNING: Missing a blank line after declarations

Signed-off-by: Yeliz Taneroglu <yeliztaneroglu@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>