mm: cma: debugfs interface

I've noticed that there is no interfaces exposed by CMA which would let me
fuzz what's going on in there.

This small patchset exposes some information out to userspace, plus adds
the ability to trigger allocation and freeing from userspace.

This patch (of 3):

Implement a simple debugfs interface to expose information about CMA areas
in the system.

Useful for testing/sanity checks for CMA since it was impossible to
previously retrieve this information in userspace.

Change-Id: Idf4fa2c58503a6aa46f70caa01048e24ec9447f3
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: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Git-commit: 28b24c1fc8c22cabe5b8a16ffe6a61dfce51a1f2
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git


[lmark@codeaurora.org: resolve trivial merge conflicts]
Signed-off-by: Liam Mark <lmark@codeaurora.org>