x86/pci-calgary: Fix iommu_free() comparison of unsigned expression >= 0

x86/pci-calgary: Fix iommu_free() comparison of unsigned expression >= 0

commit 8fd524b355da ("x86: Kill bad_dma_address variable") has killed
bad_dma_address variable and used instead of macro DMA_ERROR_CODE
which is always zero. Since dma_addr is unsigned, the statement

   dma_addr >= DMA_ERROR_CODE

is always true, and not needed.

arch/x86/kernel/pci-calgary_64.c: In function ‘iommu_free’:
arch/x86/kernel/pci-calgary_64.c:299:2: warning: comparison of unsigned expression >= 0 is always true [-Wtype-limits]
  if (unlikely((dma_addr >= DMA_ERROR_CODE) && (dma_addr < badend))) {

Fixes: 8fd524b355da ("x86: Kill bad_dma_address variable")
Signed-off-by: Nikola Pajkovsky <npajkovsky@suse.cz>
Cc: iommu@lists.linux-foundation.org
Cc: Jon Mason <jdmason@kudzu.us>
Cc: Muli Ben-Yehuda <mulix@mulix.org>
Link: http://lkml.kernel.org/r/7612c0f9dd7c1290407dbf8e809def922006920b.1479161177.git.npajkovsky@suse.cz
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>