powerpc/mm: Parenthesise IS_ENABLED() in if condition

Currently IS_ENABLED() produces an expression surrounded by parentheses,
which allows this code to compile, generating eg:

    else if (1 || 0)
        hpte_init_native();

However a change to the macro in the kbuild tree will break this in
future by removing the parentheses.

Fixes: 7353644f ("powerpc/mm: Fix build break when PPC_NATIVE=n")
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/mm/hash_utils_64.c

@@ -926,7 +926,7 @@ void __init hash__early_init_mmu(void)
 		ps3_early_mm_init();
 	else if (firmware_has_feature(FW_FEATURE_LPAR))
 		hpte_init_pseries();
-	else if IS_ENABLED(CONFIG_PPC_NATIVE)
+	else if (IS_ENABLED(CONFIG_PPC_NATIVE))
 		hpte_init_native();
 
 	if (!mmu_hash_ops.hpte_insert)