cleanup and fix swiotlb sizing

[Christoph Hellwig]

Hi all,

based on a report from Tom that overriding the default sizing provided
by the x86 SEV code on the command line doesn't work anymore, this series
cleans up how we handle default and command line sizes for the swiotlb
buffer and then fixes the recently introduced bug in a straight-forward
way.

Diffstat:
 arch/mips/cavium-octeon/dma-octeon.c      |   16 +--------------
 arch/mips/include/asm/octeon/pci-octeon.h |    1 
 arch/mips/pci/pci-octeon.c                |    2 -
 arch/powerpc/platforms/pseries/svm.c      |   13 ++----------
 drivers/xen/swiotlb-xen.c                 |    2 -
 include/linux/swiotlb.h                   |    2 -
 kernel/dma/swiotlb.c                      |   32 +++++++++++++++---------------
 7 files changed, 25 insertions(+), 43 deletions(-)