GRU driver: minor updates

A few minor updates for the GRU driver.
	- documentation changes found in code reviews
	- changes to #ifdefs to make them recognized by "unifdef"
	  (used in simulator testing)
	- change GRU context load/unload to prefetch data

[akpm@linux-foundation.org: fix typo in comment]
Signed-off-by: Jack Steiner <steiner@sgi.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>