UBUNTU: SAUCE: Do not build the xr-usb-serial driver for s390

Signed-off-by: Brad Figg <brad.figg@canonical.com>

ubuntu/Makefile

@@ -26,14 +26,13 @@ obj-$(CONFIG_DRM_I915_BPO)	+= i915/
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 obj-$(CONFIG_HIO)             += hio/
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+ifeq ($(filter $(ARCH), s390),)
 obj-y				+= xr-usb-serial/
+endif
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