Do not compile nuvoton superio for all board

The nuvoton WPCM450 code is compiled for all boards regardless of
whether or not they use it. Compile it only for boards needing it.

Change-Id: Iaf4cf2c479eb3238863f0771be799f02a8cc3421
Signed-off-by: Alexandru Gagniuc <mr.nuke.me@gmail.com>
Reviewed-on: http://review.coreboot.org/129
Tested-by: build bot (Jenkins)
Reviewed-by: Kerry She <shekairui@gmail.com>
Reviewed-by: Marc Jones <marcj303@gmail.com>

src/mainboard/supermicro/h8qgi/Kconfig

@@ -28,6 +28,7 @@ config BOARD_SPECIFIC_OPTIONS
 	select SOUTHBRIDGE_AMD_SR5650
 	select SOUTHBRIDGE_AMD_SP5100
 	select SUPERIO_WINBOND_W83627DHG
+	select SUPERIO_NUVOTON_WPCM450
 	select BOARD_HAS_FADT
 	select HAVE_BUS_CONFIG
 	select HAVE_OPTION_TABLE

src/mainboard/supermicro/h8scm_fam10/Kconfig

@@ -10,6 +10,7 @@ config BOARD_SPECIFIC_OPTIONS # dummy
 	select SOUTHBRIDGE_AMD_SR5650
 	select SOUTHBRIDGE_AMD_SP5100
 	select SUPERIO_WINBOND_W83627HF
+	select SUPERIO_NUVOTON_WPCM450
 	select HAVE_BUS_CONFIG
 	select HAVE_OPTION_TABLE
 	select GENERATE_PIRQ_TABLE

src/superio/nuvoton/Makefile.inc

@@ -17,4 +17,4 @@
 ## Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301 USA
 ##
 
-subdirs-y += wpcm450
+subdirs-$(CONFIG_SUPERIO_NUVOTON_WPCM450) += wpcm450