target-ppc: do not make PowerPCCPUClass depend on target-specific symbols

Just leave some members in even if they are unused on e.g.
32-bit PPC or user-mode emulation.  This avoids complications
when using PowerPCCPUClass in code that is compiled just
once (because it applies to both 32-bit and 64-bit PPC
for example) but still needs to peek at PPC-specific members.
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

target-ppc/cpu-qom.h

@@ -67,14 +67,10 @@ typedef struct PowerPCCPUClass {
     uint32_t flags;
     int bfd_mach;
     uint32_t l1_dcache_size, l1_icache_size;
-#if defined(TARGET_PPC64)
     const struct ppc_segment_page_sizes *sps;
-#endif
     void (*init_proc)(CPUPPCState *env);
     int  (*check_pow)(CPUPPCState *env);
-#if defined(CONFIG_SOFTMMU)
     int (*handle_mmu_fault)(PowerPCCPU *cpu, vaddr eaddr, int rwx, int mmu_idx);
-#endif
     bool (*interrupts_big_endian)(PowerPCCPU *cpu);
 } PowerPCCPUClass;