KVM: PPC: BOOKE: Add one_reg documentation of SPRG9 and DBSR

This was missed in respective one_reg implementation patch.
Signed-off-by: Bharat Bhushan <Bharat.Bhushan@freescale.com>
Signed-off-by: Alexander Graf <agraf@suse.de>

Documentation/virtual/kvm/api.txt

@@ -1901,6 +1901,8 @@ registers, find a list below:
   PPC   | KVM_REG_PPC_ARCH_COMPAT       | 32
   PPC   | KVM_REG_PPC_DABRX             | 32
   PPC   | KVM_REG_PPC_WORT              | 64
+  PPC	| KVM_REG_PPC_SPRG9             | 64
+  PPC	| KVM_REG_PPC_DBSR              | 32
   PPC   | KVM_REG_PPC_TM_GPR0           | 64
           ...
   PPC   | KVM_REG_PPC_TM_GPR31          | 64