powerpc: Add myself to MAINTAINERS for Power VFIO support

Signed-off-by: Timothy Pearson <tpearson@raptorengineering.com>
Acked-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/256219069.16998525.1678123888896.JavaMail.zimbra@raptorengineeringinc.com