frv: move HAVE_ARCH_UNMAPPED_AREA to pgtable.h

it has no business in uaccess.h, everything else has it in pgtable.h and
the only user (mm/mmap.c) unconditionally pulls asm/pgtable.h via linux/mm.h.

Signed-off-by: Al Viro <[e-mail]>

arch/frv/include/asm/pgtable.h

···
 #ifndef __ASSEMBLY__
 extern void __init paging_init(void);
 #endif /* !__ASSEMBLY__ */
+#define HAVE_ARCH_UNMAPPED_AREA
 
 #endif /* _ASM_PGTABLE_H */

arch/frv/include/asm/uaccess.h

···
 #include <asm/segment.h>
 #include <asm/sections.h>
 
-#define HAVE_ARCH_UNMAPPED_AREA	/* we decide where to put mmaps */
-
 #define __ptr(x) ((unsigned long __force *)(x))
 
 #define VERIFY_READ	0