rtl8192u: fix whitespace after '(' and before ')' in r8192U_core.c

This patch removes whitespace after '(' and before ')'
following the kernel coding style.

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