x86/vLAPIC: avoid speculative out of bounds accesses

x86/vLAPIC: avoid speculative out of bounds accesses

Array indexes used in the MSR read/write emulation functions as well as
the direct VMX / APIC-V hook are derived from guest controlled values.
Restrict their ranges to limit the side effects of speculative
execution.

Along these lines also constrain the vlapic_lvt_mask[] access.

Remove the unused vlapic_lvt_{vector,dm}() instead of adjusting them.

This is part of the speculative hardening effort.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Andrew Cooper <andrew.cooper3@citrix.com>