greybus: kernel_ver.h: fix leading space coding style issues

When cutting and pasting some of the ATTR macros into kernel_ver.h, I
dropped the tabs.  Fix this up and make checkpatch.pl happy.
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>
Reviewed-by: Viresh Kumar <viresh.kumar@linaro.org>