ANDROID: GKI: dma-coherent: Expose device base address and size

Allow clients to be able to determine the device base address and
size of a dma coherent memory region.

This is required for clients that want to explicitly manage that memory.

Change-Id: I3e5b721d9d318526422ec26995cc1af7b7f04077
Signed-off-by: Liam Mark <lmark@codeaurora.org>
(cherry picked from commit 63585739d1881d987c0c0f06199cf749ad62c6d1)
Bug: 155522481
Signed-off-by: Mark Salyzyn <salyzyn@google.com>
[saravanak conflict resolution due to file move and Change EXPORT_SYMBOL
to EXPORT_SYMBOL_GPL]
Signed-off-by: Saravana Kannan <saravanak@google.com>