target/ppc: Fix compilation with FLUSH_ALL_TLBS debug option

target/ppc: Fix compilation with FLUSH_ALL_TLBS debug option

../target/ppc/mmu_helper.c: In function 'helper_store_ibatu':
../target/ppc/mmu_helper.c:1802:17: error: unused variable 'cpu' [-Werror=unused-variable]
 1802 |     PowerPCCPU *cpu = env_archcpu(env);
      |                 ^~~
../target/ppc/mmu_helper.c: In function 'helper_store_dbatu':
../target/ppc/mmu_helper.c:1838:17: error: unused variable 'cpu' [-Werror=unused-variable]
 1838 |     PowerPCCPU *cpu = env_archcpu(env);
      |                 ^~~
../target/ppc/mmu_helper.c: In function 'helper_store_601_batu':
../target/ppc/mmu_helper.c:1874:17: error: unused variable 'cpu' [-Werror=unused-variable]
 1874 |     PowerPCCPU *cpu = env_archcpu(env);
      |                 ^~~
../target/ppc/mmu_helper.c: In function 'helper_store_601_batl':
../target/ppc/mmu_helper.c:1919:17: error: unused variable 'cpu' [-Werror=unused-variable]
 1919 |     PowerPCCPU *cpu = env_archcpu(env);

Fixes: db70b31144 ("target/ppc: Use env_cpu, env_archcpu")
Signed-off-by: Fabiano Rosas <farosas@linux.ibm.com>
Message-Id: <20210702215235.1941771-3-farosas@linux.ibm.com>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>