cma: increase CMA_ALIGNMENT upper limit to 12

Some systems require a larger maximum PAGE_SIZE order for CMA allocations.
 To accommodate such systems, increase the upper-bound of the
CMA_ALIGNMENT range to 12 (which ends up being 16MB on systems with 4K
pages).

Signed-off-by: Marc Carino <marc.ceeeee@gmail.com>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>