The generic iomap library needs to be linked unconditionally.

Otherwise modules that get loaded dynamically will not be able
to resolve the iomap functions, if no built-in drivers caused
it to be linked in at compile-time.

lib/Makefile

@@ -10,7 +10,6 @@ lib-y := errno.o ctype.o string.o vsprintf.o cmdline.o \
 
 lib-$(CONFIG_RWSEM_GENERIC_SPINLOCK) += rwsem-spinlock.o
 lib-$(CONFIG_RWSEM_XCHGADD_ALGORITHM) += rwsem.o
-lib-$(CONFIG_GENERIC_IOMAP) += iomap.o
 
 ifneq ($(CONFIG_HAVE_DEC_LOCK),y) 
   lib-y += dec_and_lock.o
@@ -19,6 +18,7 @@ endif
 obj-$(CONFIG_CRC_CCITT)	+= crc-ccitt.o
 obj-$(CONFIG_CRC32)	+= crc32.o
 obj-$(CONFIG_LIBCRC32C)	+= libcrc32c.o
+obj-$(CONFIG_GENERIC_IOMAP) += iomap.o
 
 obj-$(CONFIG_ZLIB_INFLATE) += zlib_inflate/
 obj-$(CONFIG_ZLIB_DEFLATE) += zlib_deflate/