savevm: Add VMSTATE_UINT64_EQUAL helpers

The savevm code already includes a number of *_EQUAL helpers which act as
sanity checks verifying that the configuration of the saved state matches
that of the machine we're loading into to work.  Variants already exist
for 8 bit 16 bit and 32 bit integers, but not 64 bit integers.  This patch
fills that hole, adding a UINT64 version.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Juan Quintela <quintela@redhat.com>
