x86/build: Move exception tables into __ro_after_init

x86/build: Move exception tables into __ro_after_init

Since c/s 79713ed0a94c ("x86: move both exception tables into .rodata") in
2016, we've been (ab)using the fact that .rodata is read/write during early
boot, so we can sort the two tables.

Now that we have a real __ro_after_init concept, reposition them to better
match reality.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
---
CC: Jan Beulich <JBeulich@suse.com>
CC: Roger Pau Monné <roger.pau@citrix.com>
CC: Wei Liu <wl@xen.org>