Staging: btmtk_usb: Fix incorrect brace placement

The patch fixes the following checkpatch.pl warning in btmtk_usb.c
WARNING: braces {} are not necessary for single statement blocks

Signed-off-by: Rashika Kheria <rashika.kheria@gmail.com>
Reviewed-by: Zach Brown <zab@redhat.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>