dirtylimit.c just uses one TARGET_PAGE_SIZE macro - change it to
qemu_target_page_size() so we can move thefile into the target
independent source set. Then we only have to compile this file
once during the build instead of multiple times (one time for
each target).

Message-Id: <20230413054509.54421-1-thuth@redhat.com>
Reviewed-by: Fabiano Rosas <farosas@suse.de>
Signed-off-by: Thomas Huth <thuth@redhat.com>