target/i386: Correct implementation for FCS, FIP, FDS and FDP

target/i386: Correct implementation for FCS, FIP, FDS and FDP

Update FCS:FIP and FDS:FDP according to the Intel Manual Vol.1 8.1.8.
Note that CPUID.(EAX=07H,ECX=0H):EBX[bit 13] is not implemented by
design in this patch and will be added along with TCG features flag
in a separate patch later.

Signed-off-by: Ziqiao Kong <ziqiaokong@gmail.com>
Message-Id: <20210530150112.74411-2-ziqiaokong@gmail.com>
[rth: Push FDS/FDP handling down into mod != 3 case; free last_addr.]
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>