bitops: rename for_each_bit() to for_each_set_bit(): mtd

Rename for_each_bit() to for_each_set_bit in the kernel source tree.  To
permit for_each_clear_bit(), should that ever be added.

I'll be sending a patch to Linus this week which removes the temporary
for_each_bit() macro, so this patch will be needed to avoid build
breakage.

Suggested-by: Alexey Dobriyan <adobriyan@gmail.com>
Suggested-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Russell King <rmk@arm.linux.org.uk>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Artem Bityutskiy <dedekind@infradead.org>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>