powerpc/85xx: add hypervisor config entries to corenet_smp_defconfig

CONFIG_PPC_EPAPR_HV_BYTECHAN adds support for the Freescale hypervisor
byte channel tty driver.

CONFIG_VIRT_DRIVERS and CONFIG_FSL_HV_MANAGER add support for the Freescale
hypervisor management driver.

Signed-off-by: Timur Tabi <timur@freescale.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>