Update Maintainers for IBM Power 842, vscsi, and vfc drivers

Update the MAINTAINERS file to indicate the current maintainers
for the IBM Power 842 Compression driver, IBM Power Virtual SCSI
driver and the IBM Power Virtual FC Driver.

Signed-off-by: Nathan Fontenot <nfont@linux.vnet.ibm.com>
Acked-by: Brian King <brking@linux.vnet.ibm.com>
Acked-by: Robert Jennings <rob@pochix.net>
Signed-off-by: Christoph Hellwig <hch@lst.de>