staging: greybus: firmware: Remove extra braces from single line if

Fixes checkpatch warning:
  braces {} are not necessary for any arm of this statement

Signed-off-by: Michael Sartain <mikesart@fastmail.com>
Acked-by: Viresh Kumar <viresh.kumar at linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>