KVM: selftests: Expose align() helpers to tests

Refactor align() to work with non-pointers and split into separate
helpers for aligning up vs. down. Add align_ptr_up() for use with
pointers. Expose all helpers so that they can be used by tests and/or
other utilities.  The align_down() helper in particular will be used to
ensure gpa alignment for hugepages.

No functional change intended.

[Added sepearate up/down helpers and replaced open-coded alignment
 bit math throughout the KVM selftests.]

Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: David Matlack <dmatlack@google.com>
Reviewed-by: Ben Gardon <bgardon@google.com>
Message-Id: <20211111000310.1435032-3-dmatlack@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>