move arch/sh/lib/io.o to obj-y

EXPORT_SYMBOL's in lib-y considered harmful:

<--  snip  -->

...
  MODPOST 1837 modules
ERROR: "__raw_readsl" [drivers/ssb/ssb.ko] undefined!
ERROR: "__raw_writesl" [drivers/ssb/ssb.ko] undefined!
ERROR: "__raw_writesl" [drivers/net/smc91x.ko] undefined!
ERROR: "__raw_readsl" [drivers/net/smc91x.ko] undefined!
ERROR: "__raw_writesl" [drivers/net/3c59x.ko] undefined!
ERROR: "__raw_readsl" [drivers/net/3c59x.ko] undefined!
...
make[2]: *** [__modpost] Error 1

<--  snip  -->
Reported-by: Adrian Bunk <bunk@kernel.org>
Signed-off-by: Adrian Bunk <bunk@kernel.org>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>

arch/sh/lib/Makefile

@@ -2,9 +2,11 @@
 # Makefile for SuperH-specific library files..
 #
 
-lib-y  = delay.o io.o memset.o memmove.o memchr.o \
+lib-y  = delay.o memset.o memmove.o memchr.o \
 	 checksum.o strlen.o div64.o div64-generic.o
 
+obj-y				+= io.o
+
 memcpy-y			:= memcpy.o
 memcpy-$(CONFIG_CPU_SH4)	:= memcpy-sh4.o