Fixes gcc '-Wunused-but-set-variable' warning:

arch/powerpc/kvm/emulate_loadstore.c: In function kvmppc_emulate_loadstore:
arch/powerpc/kvm/emulate_loadstore.c:87:6: warning: variable ra set but not used [-Wunused-but-set-variable]
arch/powerpc/kvm/emulate_loadstore.c: In function kvmppc_emulate_loadstore:
arch/powerpc/kvm/emulate_loadstore.c:87:10: warning: variable rs set but not used [-Wunused-but-set-variable]
arch/powerpc/kvm/emulate_loadstore.c: In function kvmppc_emulate_loadstore:
arch/powerpc/kvm/emulate_loadstore.c:87:14: warning: variable rt set but not used [-Wunused-but-set-variable]

They are not used since commit 2b33cb58 ("KVM: PPC: Reimplement
LOAD_FP/STORE_FP instruction mmio emulation with analyse_instr() input")
Reported-by: NHulk Robot <hulkci@huawei.com>
Signed-off-by: Nzhengbin <zhengbin13@huawei.com>
Signed-off-by: NPaul Mackerras <paulus@ozlabs.org>