checkpatch: Add BLOCK_COMMENT_STYLE to ignore list

Linux' newest checkpatch.pl flags comments like these:

/* This is a concise 2-line comment that explains what the code does in
 * sufficient detail without wasting too much vertical space. */
do_stuff_that_needs_explaining();

Comments like these have been used in our code base for a long time and
I don't think we should disallow them now. Ending the comment on the
same line doesn't really hurt readability and wastes less screen real
estate (which in turn usually helps overall code comprehension).

Change-Id: Ifd57f3d3a62738165024cb4b2e75a4f815a57922
Signed-off-by: Julius Werner <jwerner@chromium.org>
Reviewed-on: https://review.coreboot.org/16060
Tested-by: build bot (Jenkins)
Reviewed-by: Patrick Georgi <pgeorgi@google.com>

.checkpatch.conf

@@ -14,3 +14,4 @@
 --ignore PREFER_PACKED
 --ignore PREFER_PRINTF
 --ignore SPLIT_STRING
+--ignore BLOCK_COMMENT_STYLE