powerpc/mm: Compile out radix related functions if RADIX_MMU is disabled

Currently we depend on mmu_has_feature to evalute to zero based on
MMU_FTRS_POSSIBLE mask. In a later patch, we want to update
radix_enabled() to runtime update the conditional operation to a jump
instruction. This implies we cannot depend on MMU_FTRS_POSSIBLE mask.
Instead define radix_enabled to return 0 if RADIX_MMU is not enabled.
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/include/asm/book3s/64/mmu.h

@@ -23,7 +23,12 @@ struct mmu_psize_def {
 };
 extern struct mmu_psize_def mmu_psize_defs[MMU_PAGE_COUNT];
 
+#ifdef CONFIG_PPC_RADIX_MMU
 #define radix_enabled() mmu_has_feature(MMU_FTR_RADIX)
+#else
+#define radix_enabled() (0)
+#endif
+
 
 #endif /* __ASSEMBLY__ */