drm/i2c: give i2c it's own Kconfig

Move this out of nouveau directory.  As we start to add more encoder
slaves used by other drivers, it makes sense to put the Kconfig bits in
one place.

Signed-off-by: Rob Clark <robdclark@gmail.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig
index 3399b20..ed9e3af 100644
--- a/drivers/gpu/drm/Kconfig
+++ b/drivers/gpu/drm/Kconfig
@@ -69,6 +69,8 @@
 	help
 	  Choose this if you need the KMS CMA helper functions
 
+source "drivers/gpu/drm/i2c/Kconfig"
+
 config DRM_TDFX
 	tristate "3dfx Banshee/Voodoo3+"
 	depends on DRM && PCI