migration/vmstate: renames in (load|save)_state

migration/vmstate: renames in (load|save)_state

The vmstate_(load|save)_state start out with an a void *opaque pointing
to some struct, and manipulate one or more elements of one field within
that struct.

First the field within the struct is pinpointed as opaque + offset, then
if this is a pointer the pointer is dereferenced to obtain a pointer to
the first element of the vmstate field. Pointers to further elements if
any are calculated as first_element + i * element_size (where i is the
zero based index of the element in question).

Currently base_addr and addr is used as a variable name for the pointer
to the first element and the pointer to the current element being
processed. This is suboptimal because base_addr is somewhat
counter-intuitive (because obtained as base + offset) and both base_addr
and addr not very descriptive (that we have a pointer should be clear
from the fact that it is declared as a pointer).

Let make things easier to understand by renaming base_addr to first_elem
and addr to curr_elem. This has the additional benefit of harmonizing
with other names within the scope (n_elems, vmstate_n_elems).

Signed-off-by: Halil Pasic <pasic@linux.vnet.ibm.com>
Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Message-Id: <20170222160119.52771-2-pasic@linux.vnet.ibm.com>
Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>