gru: change context load and unload

Remove "static" from the functions for loading/unloading GRU contexts.
These functions will be called from other GRU files.  Fix bug in unlocking
gru context.

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>