hmm cleanups, v2

[Christoph Hellwig]

Hi Jérôme, Ben, Felix and Jason,

below is a series against the hmm tree which cleans up various minor
bits and allows HMM_MIRROR to be built on all architectures.

Diffstat:

    11 files changed, 94 insertions(+), 210 deletions(-)

A git tree is also available at:

    git://git.infradead.org/users/hch/misc.git hmm-cleanups.2

Gitweb:

    http://git.infradead.org/users/hch/misc.git/shortlog/refs/heads/hmm-cleanups.2

Changes since v1:
 - fix the cover letter subject
 - improve various patch descriptions
 - use svmm->mm in nouveau_range_fault
 - inverse the hmask field when using it
 - select HMM_MIRROR instead of making it a user visible option