firmware/dmi_scan: fix most checkpatch errors and warnings

Fix all errors and trivial warnings reported by checkpatch for file
drivers/firmware/dmi_scan.c.

Signed-off-by: Jean Delvare <jdelvare@suse.de>
Cc: Joe Perches <joe@perches.com>
Cc: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>