rtl8192u: fix whitespace around ',' in r8192U_core.c

This patch fixes whitespace around ',' and corrects
the following checkpatch error:
ERROR: space required after that ','

Signed-off-by: Xenia Ragiadakou <burzalodowa@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>