accel/habanalabs: support mapping cb with vmalloc-backed coherent memory
When IOMMU is enabled, dma_alloc_coherent() with GFP_USER may return
addresses from the vmalloc range. If such an address is mapped without
VM_MIXEDMAP, vm_insert_page() will trigger a BUG_ON due to the
VM_PFNMAP restriction.
Fix this by checking for vmalloc addresses and setting VM_MIXEDMAP
in the VMA before mapping. This ensures safe mapping and avoids kernel
crashes. The memory is still driver-allocated and cannot be accessed
directly by userspace.