ANDROID: Add EXPORT_SYMBOL_GPL for dma_heap_get_name

Upstream has no modules that use it, but in common
we system/cma/etc are modular, so we need to export
the new dma_heap_get_name() symbol

Signed-off-by: John Stultz <john.stultz@linaro.org>
Bug: 167709539
Change-Id: I25d77467742ea9c309c909874e0f1e9adf8a64af