ion: Add carveout and chunk heaps to dummy driver

Add support to the dummy driver for basic carveout and chunk heaps.

Since we're generating these heaps at module_init, and we want
this driver to be generic enough to be tested on any arch, we
don't have the ability to alloc bootmem, so both of these heaps
are conventionally allocated using alloc_pages(), which limits us
to 4M in size.

Should look into using CMA for heap allocation eventually, but
this provides enough to test the basic functionality of the
heaps.

Cc: Colin Cross <ccross@android.com>
Cc: Greg KH <gregkh@linuxfoundation.org>
Cc: Jesse Barker <jesse.barker@arm.com>
Cc: Android Kernel Team <kernel-team@android.com>
Signed-off-by: John Stultz <john.stultz@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>