powerpc: Add KVM as module to defconfigs

Add HV mode KVM to Book3 server 64bit defconfigs as a module.

Doesn't add much to the size:
   text	   data	    bss	     dec	    hex	filename
8244109	4686767	 994000	13924876	 d47a0c	vmlinux.vanilla
8256092 4691607  994128 13941827         d4bc43 vmlinux.kvm

This should enable more testing of this configuration.

Signed-off-by: Michael Neuling <mikey@neuling.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>