x86: remove ifdef CONFIG_CALGARY_IOMMU in pci-dma.c

asm-x86/calgary.h has dummy calgary_iommu_init() and detect_calgary()
in !CONFIG_CALGARY_IOMMU case. So we don't need ifdef
CONFIG_CALGARY_IOMMU in pci-dma.c.

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Acked-by: Muli Ben-Yehuda <muli@il.ibm.com>
Cc: Alexis Bruemmer <alexisb@us.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>