Add gcc attribute unused to variable tmp. Fix warning treated as error with
W=1:

   arch/powerpc/kernel/kvm.c:675:6: error: variable ‘tmp’ set but not used [-Werror=unused-but-set-variable]

Signed-off-by: Mathieu Malaterre <redacted>
---
  arch/powerpc/kernel/kvm.c | 2 +-
  1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/powerpc/kernel/kvm.c b/arch/powerpc/kernel/kvm.c
index 9ad37f827a97..cd3c088283f9 100644
--- a/arch/powerpc/kernel/kvm.c
+++ b/arch/powerpc/kernel/kvm.c

@@ -672,7 +672,7 @@ static void kvm_use_magic_page(void)
  {
  	u32 *p;
  	u32 *start, *end;
-	u32 tmp;
+	u32 tmp __maybe_unused;
  	u32 features;
  
  	/* Tell the host to map the magic page to -4096 on all CPUs */