staging: r8188eu: Add line after declarations

Reported by checkpatch:

WARNING: Missing a blank line after declarations

Acked_by: Larry Finger <Larry.Finger@lwfinger.net>
Signed-off-by: Alaa Mohamed <eng.alaamohamedsoliman.am@gmail.com>
Link: https://lore.kernel.org/r/19d8f316e43d16c9341f7fe94e68534cf60cc05c.1649082939.git.eng.alaamohamedsoliman.am@gmail.com


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