powerpc/bpf: Fix warning for unused ori31_emitted

Without this, the compiler (clang21) might emit a warning under W=1
because the variable ori31_emitted is set but never used if
CONFIG_PPC_BOOK3S_64=n.

Without this patch:

$ make -j $(nproc) W=1 ARCH=powerpc SHELL=/bin/bash arch/powerpc/net
  [...]
  CC      arch/powerpc/net/bpf_jit_comp.o
  CC      arch/powerpc/net/bpf_jit_comp64.o
../arch/powerpc/net/bpf_jit_comp64.c: In function 'bpf_jit_build_body':
../arch/powerpc/net/bpf_jit_comp64.c:417:28: warning: variable 'ori31_emitted' set but not used [-Wunused-but-set-variable]
  417 |         bool sync_emitted, ori31_emitted;
      |                            ^~~~~~~~~~~~~
  AR      arch/powerpc/net/built-in.a

With this patch:

  [...]
  CC      arch/powerpc/net/bpf_jit_comp.o
  CC      arch/powerpc/net/bpf_jit_comp64.o
  AR      arch/powerpc/net/built-in.a

Fixes: dff883d ("bpf, arm64, powerpc: Change nospec to include v1 barrier")
Reported-by: kernel test robot <[email protected]>
Closes: https://lore.kernel.org/oe-kbuild-all/[email protected]/
Signed-off-by: Luis Gerhorst <[email protected]>
Reviewed-by: Christophe Leroy <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Alexei Starovoitov <[email protected]>

Author: luisgerhorst

arch/powerpc/net/bpf_jit_comp64.c

@@ -820,13 +820,12 @@ int bpf_jit_build_body(struct bpf_prog *fp, u32 *image, u32 *fimage, struct code
 		case BPF_ST | BPF_NOSPEC:
 			sync_emitted = false;
 			ori31_emitted = false;
-#ifdef CONFIG_PPC_E500
-			if (!bpf_jit_bypass_spec_v1()) {
+			if (IS_ENABLED(CONFIG_PPC_E500) &&
+			    !bpf_jit_bypass_spec_v1()) {
 				EMIT(PPC_RAW_ISYNC());
 				EMIT(PPC_RAW_SYNC());
 				sync_emitted = true;
 			}
-#endif
 			if (!bpf_jit_bypass_spec_v4()) {
 				switch (stf_barrier) {
 				case STF_BARRIER_EIEIO:
@@ -849,10 +848,10 @@ int bpf_jit_build_body(struct bpf_prog *fp, u32 *image, u32 *fimage, struct code
 					break;
 				}
 			}
-#ifdef CONFIG_PPC_BOOK3S_64
-			if (!bpf_jit_bypass_spec_v1() && !ori31_emitted)
+			if (IS_ENABLED(CONFIG_PPC_BOOK3S_64) &&
+			    !bpf_jit_bypass_spec_v1() &&
+			    !ori31_emitted)
 				EMIT(PPC_RAW_ORI(_R31, _R31, 0));
-#endif
 			break;
 
 		/*