KVM: SVM: fix emulation of msr reads/writes of MSR_FS_BASE and MSR_GS_BASE

KVM: SVM: fix emulation of msr reads/writes of MSR_FS_BASE and MSR_GS_BASE

If these msrs are read by the emulator (e.g due to 'force emulation' prefix),
SVM code currently fails to extract the corresponding segment bases,
and return them to the emulator.

Fix that.

Cc: stable@vger.kernel.org
Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
Link: https://lore.kernel.org/r/20240802151608.72896-3-mlevitsk@redhat.com
Signed-off-by: Sean Christopherson <seanjc@google.com>