staging: greybus: minor code style fix

checkpatch warning fix for string split across lines

Signed-off-by: Manikantan Ravichandran <ravman1991@gmail.com>
Link: https://lore.kernel.org/r/20210212225035.GA16260@whach


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>