staging: rtl8723bs: Add space between elements

Concatenated strings should use spaces between elements.
Issue found by checkpatch.

Signed-off-by: Javier F. Arias <jarias.linux@gmail.com>
Link: https://lore.kernel.org/r/a2387d4c10c2ed0cbca9d5c7ded424892452178f.1570577926.git.jarias.linux@gmail.com


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