staging: greybus: fix checkpatch braces not necessary warning

Fix the following warnings:
braces {} are not necessary for any arm of this statement

Signed-off-by: Abdul Rauf <abdulraufmujahid@gmail.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>