lib/bitmap.c: guard exotic bitmap functions by CONFIG_NUMA

The bitmap_remap, _bitremap, _onto and _fold functions are only used,
via their node_ wrappers, in mm/mempolicy.c, which is only built for
CONFIG_NUMA.  The helper bitmap_ord_to_pos used by these functions is
global, but its only external caller is node_random() in lib/nodemask.c,
which is also guarded by CONFIG_NUMA.

For !CONFIG_NUMA:

add/remove: 0/6 grow/shrink: 0/0 up/down: 0/-621 (-621)
Function                                     old     new   delta
bitmap_pos_to_ord                             20       -     -20
bitmap_ord_to_pos                             70       -     -70
bitmap_bitremap                               81       -     -81
bitmap_fold                                  113       -    -113
bitmap_onto                                  123       -    -123
bitmap_remap                                 214       -    -214
Total: Before=4776, After=4155, chg -13.00%

Link: http://lkml.kernel.org/r/20190329205353.6010-2-linux@rasmusvillemoes.dk
Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Andy Shevchenko <andy.shevchenko@gmail.com>
Cc: Yury Norov <yury.norov@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

lib/bitmap.c

@@ -649,6 +649,7 @@ int bitmap_parselist_user(const char __user *ubuf,
 EXPORT_SYMBOL(bitmap_parselist_user);
 
 
+#ifdef CONFIG_NUMA
 /**
  * bitmap_pos_to_ord - find ordinal of set bit at given position in bitmap
  *	@buf: pointer to a bitmap
@@ -952,6 +953,7 @@ void bitmap_fold(unsigned long *dst, const unsigned long *orig,
 	for_each_set_bit(oldbit, orig, nbits)
 		set_bit(oldbit % sz, dst);
 }
+#endif /* CONFIG_NUMA */
 
 /*
  * Common code for bitmap_*_region() routines.