mm: cma: release trigger

Provides a userspace interface to trigger a CMA release.

Usage:

        echo [pages] > free

This would provide testing/fuzzing access to the CMA release paths.

Change-Id: Idcba1f7c297b768337be8cf69301a02264c3baf0
[akpm@linux-foundation.org: coding-style fixes]
[mhocko@suse.cz: fix build]
Signed-off-by: Sasha Levin <sasha.levin@oracle.com>
Acked-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: Laura Abbott <lauraa@codeaurora.org>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: Michal Hocko <mhocko@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Git-commit: 8325330b026509127d4541e0f511c0c10648c2d5
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git


Signed-off-by: Liam Mark <lmark@codeaurora.org>