target/i386: implement undocumented "smsw r32" behavior

target/i386: implement undocumented "smsw r32" behavior

In 32-bit mode, the higher 16 bits of the destination
register are undefined.  In practice CR0[31:0] is stored,
just like in 64-bit mode, so just remove the "if" that
currently differentiates the behavior.

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reported-by: Roman Bolshakov <r.bolshakov@yadro.com>
Reviewed-by: Roman Bolshakov <r.bolshakov@yadro.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>