crypto/nx/nx-842: Fix handling of vmalloc addresses
The powerpc specific nx-842 compression driver does not currently
handle translating a vmalloc address to a physical address.
The current driver uses __pa() for all addresses which does not
properly handle vmalloc addresses and thus causes a failure since
we do not pass a proper physical address to the hypervisor.
This patch adds a routine to convert an address to a physical
address by checking for vmalloc addresses and handling them properly.