staging: android: ion: Combine cache and uncache pools

staging: android: ion: Combine cache and uncache pools

Now we call dma_map in the dma_buf API callbacks and handle explicit
caching by the dma_buf sync API, which make cache and uncache pools
in the same handling flow, which can be combined.

Acked-by: Sumit Semwal <sumit.semwal@linaro.org>
Signed-off-by: Yisheng Xie <xieyisheng1@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>