video: tegra: nvmap: fix read failures, super user and noref pinning

video: tegra: nvmap: fix read failures, super user and noref pinning

a >= vs > error when checking the operating region of the read and
write ioctls was causing failures when reading the last byte of a handle.

the super-user node (knvmap) wasn't registered correctly due to a cut-
and-paste error, and the regular user node was assigned super-user
priveleges.

noref pinning wasn't correctly validating that the specified handle
existed before pinning it, which caused the reference count for the
handle to become imbalanced on a subsequent unpin

Change-Id: I9985b85023705b00389a53fb962c3b60d62da6b8
Signed-off-by: Gary King <gking@nvidia.com>