[ARM] Fix _find_next_bit_be prototype to use 'const' qualifier

_find_next_bit_be() does not have a 'const' qualifier for the first 
argument, so we get the following warning for a very large number
of files:

In file included from include/linux/sched.h:15,
                 from include/linux/module.h:10,
                 from drivers/mtd/maps/ixp2000.c:24:
include/linux/cpumask.h: In function `__next_cpu':
include/linux/cpumask.h:216: warning: passing arg 1 of `_find_next_bit_be' 
discards qualifiers from pointer target type
Signed-off-by: Deepak Saxena <dsaxena@plexity.net>

include/asm-arm/bitops.h

@@ -227,7 +227,7 @@ extern int _test_and_change_bit_be(int nr, volatile unsigned long * p);
 extern int _find_first_zero_bit_be(void * p, unsigned size);
 extern int _find_next_zero_bit_be(void * p, int size, int offset);
 extern int _find_first_bit_be(const unsigned long *p, unsigned size);
-extern int _find_next_bit_be(unsigned long *p, int size, int offset);
+extern int _find_next_bit_be(const unsigned long *p, int size, int offset);
 
 /*
  * The __* form of bitops are non-atomic and may be reordered.