target/s390x/tcg/mem_helper: Remove bad assert() statement

The "assert(!nonfault)" statement can be triggered by running the
"mvpg" s390x kvm-unit-test with TCG. According to Richard: "... the
assert looks backward. We should only arrive there if nonfault was
true for the probe (otherwise the probe would have raised the
exception directly).  I would think we could just remove the assert."

Fixes: 4049431478 ("target/s390x: Fix s390_probe_access for user-only")
Suggested-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20230317135737.597570-1-thuth@redhat.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>

target/s390x/tcg/mem_helper.c

@@ -149,7 +149,6 @@ static inline int s390_probe_access(CPUArchState *env, target_ulong addr,
                                    nonfault, phost, ra);
 
     if (unlikely(flags & TLB_INVALID_MASK)) {
-        assert(!nonfault);
 #ifdef CONFIG_USER_ONLY
         /* Address is in TEC in system mode; see s390_cpu_record_sigsegv. */
         env->__excp_addr = addr & TARGET_PAGE_MASK;