powerpc/mm: Define radix_enabled() in one place & use static inline

Currently we have radix_enabled() three times, twice in asm/book3s/64/mmu.h
and then a fallback in asm/mmu.h.

Consolidate them in asm/mmu.h. While we're at it convert them to be
static inlines, and change the fallback case to returning a bool, like
mmu_has_feature().

Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

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

@@ -23,13 +23,6 @@ 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_TYPE_RADIX)
-#else
-#define radix_enabled() (0)
-#endif
-
-
 #endif /* __ASSEMBLY__ */
 
 /* 64-bit classic hash table MMU */