xen/livepatch: drop load_addr Elf section field

xen/livepatch: drop load_addr Elf section field

The Elf loading logic will initially use the `data` section field to stash a
pointer to the temporary loaded data (from the buffer allocated in
livepatch_upload(), which is later relocated and the new pointer stashed in
`load_addr`.

Remove this dual field usage and use an `addr` uniformly.  Initially data will
point to the temporary buffer, until relocation happens, at which point the
pointer will be updated to the relocated address.

This avoids leaving a dangling pointer in the `data` field once the temporary
buffer is freed by livepatch_upload().

Note the `addr` field cannot retain the const attribute from the previous
`data`field, as there's logic that performs manipulations against the loaded
sections, like applying relocations or sorting the exception table.

No functional change intended.

Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
Acked-by: Michal Orzel <michal.orzel@amd.com>