MAINTAINERS: Update PARAVIRT_OPS_INTERFACE and VMWARE_HYPERVISOR_INTERFACE

Alok Kataria will be handing over VMware's maintainership of these
interfaces to Thomas Hellström, with pv-drivers as backup contact.

Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Alok Kataria <akataria@vmware.com>
Acked-by: Juergen Gross <jgross@suse.com>
Link: https://lkml.kernel.org/r/20190328120558.29897-1-thellstrom@vmware.com