target-i386: Avoid shifting left into sign bit

Add 'U' suffixes where necessary to avoid (1 << 31) which
shifts left into the sign bit, which is undefined behaviour.
Add the suffix also for other constants in the same groupings
even if they don't shift into bit 31, for consistency.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
