checkpatch: Allow longer declaration macros

Some really long declaration macros exist.

For instance;
  	DEFINE_DMA_BUF_EXPORT_INFO(exp_info);
and
	DECLARE_DM_KCOPYD_THROTTLE_WITH_MODULE_PARM(name, description)

Increase the limit from 2 words to 6 after DECLARE/DEFINE uses.

Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>