KVM: nVMX: Add a helper to encode VMCS info in MSR_IA32_VMX_BASIC

KVM: nVMX: Add a helper to encode VMCS info in MSR_IA32_VMX_BASIC

Add a helper to encode the VMCS revision, size, and supported memory types
in MSR_IA32_VMX_BASIC, i.e. when synthesizing KVM's supported BASIC MSR
value, and delete the now unused VMCS size and memtype shift macros.

For a variety of reasons, KVM has shifted (pun intended) to using helpers
to *get* information from the VMX MSRs, as opposed to defined MASK and
SHIFT macros for direct use.  Provide a similar helper for the nested VMX
code, which needs to *set* information, so that KVM isn't left with a mix
of SHIFT macros and dedicated helpers.

Reported-by: Xiaoyao Li <xiaoyao.li@intel.com>
Reviewed-by: Xiaoyao Li <xiaoyao.li@intel.com>
Reviewed-by: Kai Huang <kai.huang@intel.com>
Link: https://lore.kernel.org/r/20240605231918.2915961-8-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>