staging: android: ion: Add support for Carveout allocations in ion_alloc

Add support in ion_alloc for allocations of type ION_HEAP_TYPE_CARVEOUT
as this is required for certain audio use cases.

Change-Id: Ie300607d38173859e51b0f5421891badada594e7
Signed-off-by: Anant Goel <anantg@codeaurora.org>