powerpc/mm: drop #ifdef CONFIG_MMU in is_ioremap_addr()

powerpc always selects CONFIG_MMU and CONFIG_MMU is not checked
anywhere else in powerpc code.

Drop the #ifdef and the alternative part of is_ioremap_addr()

Fixes: 9bd3bb6 ("mm/nvdimm: add is_ioremap_addr and use that to check ioremap address")
Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/de395e444fb8dd7a6365c3314d78e15ebb3d7d1b.1566382245.git.christophe.leroy@c-s.fr

arch/powerpc/include/asm/pgtable.h

@@ -157,13 +157,9 @@ static inline bool pgd_is_leaf(pgd_t pgd)
 #define is_ioremap_addr is_ioremap_addr
 static inline bool is_ioremap_addr(const void *x)
 {
-#ifdef CONFIG_MMU
 	unsigned long addr = (unsigned long)x;
 
 	return addr >= IOREMAP_BASE && addr < IOREMAP_END;
-#else
-	return false;
-#endif
 }
 #endif /* CONFIG_PPC64 */