KVM: VMX: Inject #GP, not #UD, if SGX2 ENCLS leafs are unsupported

KVM: VMX: Inject #GP, not #UD, if SGX2 ENCLS leafs are unsupported

Per Intel's SDM, unsupported ENCLS leafs result in a #GP, not a #UD.
SGX1 is a special snowflake as the SGX1 flag is used by the CPU as a
"soft" disable, e.g. if software disables machine check reporting, i.e.
having SGX but not SGX1 is effectively "SGX completely unsupported" and
and thus #UDs.

Fixes: 9798adbc04cf ("KVM: VMX: Frame in ENCLS handler for SGX virtualization")
Cc: Binbin Wu <binbin.wu@linux.intel.com>
Cc: Kai Huang <kai.huang@intel.com>
Tested-by: Kai Huang <kai.huang@intel.com>
Reviewed-by: Kai Huang <kai.huang@intel.com>
Link: https://lore.kernel.org/r/20230405234556.696927-3-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>