Add dma_buf_heaps wsialloc implementation
requested to merge iason.paraskevopoulos/vulkan-wsi-layer:implement_dma_buf_heaps_wsialloc_allocator into main
Moves out the non ion specific code from the wsialloc ion implementation to a new wsialloc_helpers file.
Adds a dma_buf_heaps wsialloc implementation.
Renames KERNEL_DIR to KERNEL_HEADER_DIR to allow getting the kernel headers from a directory that is not coupled with the kernel source tree.
Change-Id: I7ca816b27eb7e68fd1f138ec7bda006b204c0cbe Signed-off-by: Iason Paraskevopoulos iason.paraskevopoulos@arm.com