target-i386: SSE4.2: fix pcmpXstrX instructions in "Equal each" mode

pcmpXstrX instructions in "Equal each" mode force both invalid element
pair to true. It means (upper - MAX(valids, validd)) bits should be set
to 1, not (upper - MAX(valids, validd) + 1).

Reviewed-by: Richard Henderson <rth@twiddle.net>
Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>
