powerpc/mm: Fix build error with CONFIG_PPC_TRANSACTIONAL_MEM disabled

This fix the below build error

arch/powerpc/mm/hash_utils_64.c: In function ‘flush_hash_hugepage’:
arch/powerpc/mm/hash_utils_64.c:1381:1: error: label at end of compound statement
 tm_abort:
 ^
make[1]: *** [arch/powerpc/mm/hash_utils_64.o] Error 1

Reported-by: Anshuman Khandual <khandual@linux.vnet.ibm.com>
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>