libcamera: Rename DmaHeap class to DmaBufAllocator

Users of the DmaHeap class really just want some way to allocate
dma-buffers from userspace. This can also be done by using /dev/udmabuf
instead of using /dev/dma_heap/*.

Rename DmaHeap class to DmaBufAllocator in preparation of adding
/dev/udmabuf support.

And update the DmaHeap class docs to match including replacing references
to "dma-heap type" with "dma-buf provider".

This is a pure automated rename on the code ('s/DmaHeap/DmaBufAllocator/')
+ file renames + doc updates. There are no functional changes.

The DmaBufAllocator objects in vc4.cpp and software_isp.cpp are left named
dmaHeap_ to keep the changes to those 2 files to a minimum.

Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Tested-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org> # Lenovo-x13s
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>

include/libcamera/internal/software_isp/software_isp.h

@@ -27,7 +27,7 @@
 #include <libcamera/ipa/soft_ipa_proxy.h>
 
 #include "libcamera/internal/camera_sensor.h"
-#include "libcamera/internal/dma_heaps.h"
+#include "libcamera/internal/dma_buf_allocator.h"
 #include "libcamera/internal/pipeline_handler.h"
 #include "libcamera/internal/shared_mem_object.h"
 #include "libcamera/internal/software_isp/debayer_params.h"
@@ -91,7 +91,7 @@ private:
 	Thread ispWorkerThread_;
 	SharedMemObject<DebayerParams> sharedParams_;
 	DebayerParams debayerParams_;
-	DmaHeap dmaHeap_;
+	DmaBufAllocator dmaHeap_;
 
 	std::unique_ptr<ipa::soft::IPAProxySoft> ipa_;
 };