futex: Fix hardcoded flags

Xi reported that commit 5694289c

 ("futex: Flag conversion") broke
glibc's robust futex tests.

This was narrowed down to the change of FLAGS_SHARED from 0x01 to
0x10, at which point Florian noted that handle_futex_death() has a
hardcoded flags argument of 1.

Change this to: FLAGS_SIZE_32 | FLAGS_SHARED, matching how
futex_to_flags() unconditionally sets FLAGS_SIZE_32 for all legacy
futex ops.

Reported-by: Xi Ruoyao <xry111@xry111.site>
Reported-by: Florian Weimer <fweimer@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lkml.kernel.org/r/20231114201402.GA25315@noisy.programming.kicks-ass.net
Fixes: 5694289c ("futex: Flag conversion")
Cc: <stable@vger.kernel.org>