Verify that the user specified length for a PMEM region is smaller than the size of the entire region as reported by the kernel APIs. Change-Id: Ic0dedbad0127bdaed70eafc00238b44f982b093b Signed-off-by: Jordan Crouse <jcrouse@codeaurora.org> Signed-off-by: Iliyan Malchev <malchev@google.com>