accel/ivpu: Free buffer sgt on unbind

Call dma_unmap() on all buffers before the VPU is unbinded to avoid
"device driver has pending DMA allocations while released from device"
warning when DMA-API debug is enabled.

Signed-off-by: Jacek Lawrynowicz <jacek.lawrynowicz@linux.intel.com>
Reviewed-by: Jeffrey Hugo <quic_jhugo@quicinc.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240115134434.493839-7-jacek.lawrynowicz@linux.intel.com