FMP capsule update may fail on Xavier NX platforms

[bobm21]

On Xavier NX platforms where some _b FW partitions are on an eMMC device, FMP capsule update may fail with write protect errors when updating boot chain B FW, E.g.

Overwriting active adsp-fw partition not allowed
Error writing adsp-fw, Offset=0: Write Protected
Failed to write image=adsp-fw: Write Protected

This is caused by the FwImageDxe driver loading before the FwPartitionBlockIoDxe driver which makes the _b partitions unavailable during the capsule update. A fix to the FwImageDxe Depex is being developed to ensure that the drivers load in the correct order.