bitmap: find_last_bit()

Impact: New API

As the name suggests.  For the moment everyone uses the generic one.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
diff --git a/lib/Makefile b/lib/Makefile
index 80fe8a3..32b0e64 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -37,6 +37,7 @@
 lib-$(CONFIG_RWSEM_XCHGADD_ALGORITHM) += rwsem.o
 lib-$(CONFIG_GENERIC_FIND_FIRST_BIT) += find_next_bit.o
 lib-$(CONFIG_GENERIC_FIND_NEXT_BIT) += find_next_bit.o
+lib-$(CONFIG_GENERIC_FIND_LAST_BIT) += find_last_bit.o
 obj-$(CONFIG_GENERIC_HWEIGHT) += hweight.o
 obj-$(CONFIG_LOCK_KERNEL) += kernel_lock.o
 obj-$(CONFIG_PLIST) += plist.o