greybus: greybus_trace.h: Fix dodgy indentation

We should use tabs not spaces when indenting multi-line macros and ensure
that the relevant '\' characters are aligned to each-other.

Signed-off-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>
Reviewed-by: Alex Elder <elder@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>