accel/amdxdna: Add carveout memory support for non-IOMMU systems

accel/amdxdna: Add carveout memory support for non-IOMMU systems

Add support for allocating buffers from reserved carveout memory when
IOMMU is not available. This is useful during debugging or bring-up.

In this configuration, the device uses physical addresses and does
not support scatter-gather lists, requiring physically contiguous
buffers.

Implement carveout-backed allocation and integrate it into buffer
management to support operation in physical address mode.

Signed-off-by: Max Zhen <max.zhen@amd.com>
Reviewed-by: Mario Limonciello (AMD) <superm1@kernel.org>
Signed-off-by: Lizhi Hou <lizhi.hou@amd.com>
Link: https://patch.msgid.link/20260427170949.2666601-1-lizhi.hou@amd.com