ia64: fix build failure with CONFIG_SWIOTLB

arch/ia64/kernel/pci-swiotlb.c is removed in commit 4fac8076 ("ia64: clean up swiotlb support")
but pci-swiotlb.o is still present in Makefile, and so build fail when
CONFIG_SWIOTLB is enabled.
Fix the build failure by removing pci-swiotlb.o from makefile

Fixes: 4fac8076 ("ia64: clean up swiotlb support")
Signed-off-by: Corentin Labbe <clabbe@baylibre.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>

arch/ia64/kernel/Makefile

@@ -41,7 +41,6 @@ ifneq ($(CONFIG_IA64_ESI),)
 obj-y				+= esi_stub.o	# must be in kernel proper
 endif
 obj-$(CONFIG_INTEL_IOMMU)	+= pci-dma.o
-obj-$(CONFIG_SWIOTLB)		+= pci-swiotlb.o
 
 obj-$(CONFIG_BINFMT_ELF)	+= elfcore.o