libui: update for IAllocator changes

Create an IAllocatorClient to allocate/free graphics buffers.

Test: builds and boots
Change-Id: I9978b61ee2cb6302cce34ed6d740a5616fb7e8f1
diff --git a/libs/ui/GraphicBufferAllocator.cpp b/libs/ui/GraphicBufferAllocator.cpp
index e333bc1..d258586 100644
--- a/libs/ui/GraphicBufferAllocator.cpp
+++ b/libs/ui/GraphicBufferAllocator.cpp
@@ -106,7 +106,7 @@
             PixelFormat format, uint32_t layerCount, uint32_t usage)
         : mAllocator(allocator), mBufferValid(false)
     {
-        Gralloc2::IAllocator::BufferDescriptorInfo info = {};
+        Gralloc2::IAllocatorClient::BufferDescriptorInfo info = {};
         info.width = width;
         info.height = height;
         info.format = static_cast<Gralloc2::PixelFormat>(format);