target-i386: Fix FPU helpers.

This fixes the bug that prevents x86 system images from booting
properly without KVM/HAXM. It was introduced by commit
e228840614eab80006f9d7e68339b09b3890931a which upgraded
softfloat support to upstream version.

This patch upgrades the target-i386 FPU emulation code to
always use 80-bit FPU registera, and perform computations
appropriately. This comes from upstream QEMU patch
c31da136a0bf8caad70c348f5ffc283206e9c7fc

Change-Id: I5c3452a3072f31299623b5dae754a060c86c402a
5 files changed