ppc: Let kvmppc_reset_htab() return 0 for !CONFIG_KVM

The !CONFIG_KVM implementation of kvmppc_reset_htab() returns -1
by default. Change this to return 0 so that we fall back to user space
HTAB allocation for emulated guests.

This fixes the make check failures for ppc64 emulated target.

Signed-off-by: Bharata B Rao <bharata@linux.vnet.ibm.com>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>