hw/vfio: Compile some common objects once

hw/vfio: Compile some common objects once

Some files don't rely on any target-specific knowledge
and can be compiled once:

 - helpers.c
 - container-base.c
 - migration.c (removing unnecessary "exec/ram_addr.h")
 - migration-multifd.c
 - cpr.c

Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Pierrick Bouvier <pierrick.bouvier@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Cédric Le Goater <clg@redhat.com>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Message-Id: <20250308230917.18907-4-philmd@linaro.org>
Link: https://lore.kernel.org/qemu-devel/20250311085743.21724-6-philmd@linaro.org
Signed-off-by: Cédric Le Goater <clg@redhat.com>