Fix a panic when doing non-multiples of PAGE_SIZE or misaligned transfers to a swap backed vn device.
Fix a panic when doing non-multiples of PAGE_SIZE or misaligned transfers
to a swap backed vn device.

OK'ed by:	dillon

jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase