linux: Fix a mistake in commit fb58045145

The change to futex_andl_smap() should have ordered stac before the
load from a user address, otherwise it does not fix anything.

Fixes: fb58045145 ("linux: Fix SMAP-enabled futex routines")
Sponsored by: The FreeBSD Foundation

(cherry picked from commit 60cb98a1bd2e4ea8fda532261f7211f5d4eba9c0)