i386/tcg/svm: fix incorrect canonicalization

i386/tcg/svm: fix incorrect canonicalization

For all 32-bit systems and 64-bit Windows systems, "long" is 4 bytes long.
Due to using "long" for a linear address, svm_canonicalization would
set all high bits to 1 when (assuming 48-bit linear address) the segment
base is bigger than 0x7FFF.

This fixes booting guests under TCG when the guest IDT and GDT bases are
above 0x7FFF, thereby resulting in incorrect bases. When an interrupt
arrives, it would trigger a #PF exception; the #PF would trigger again,
resulting in a #DF exception; the #PF would trigger for the third time,
resulting in triple-fault, and eventually causes a shutdown VM-Exit to
the hypervisor right after guest boot.

Cc: qemu-stable@nongnu.org
Signed-off-by: Zero Tang <zero.tangptr@gmail.com>