Confirm userfaultfd API has the required feature

It's inssufficient to confirm that UFFDIO_API userfaultfd ioctl
succeeds. We must check that the resturned features has the feature(s)
that we are interested in.

Also, remove the definition of UFFD_FEATURE_MINOR_SHMEM as
linux/userfaultfd.h now has it.

Test: atest -v CtsUffdGcTestCases
Change-Id: I367fa2a0ae026f163f0e2564a075b4d3f8ada3c0
1 file changed