x86/virt/seamldr: Initialize the newly-installed TDX module

x86/virt/seamldr: Initialize the newly-installed TDX module

Continue fleshing out the update process. At this point the new module
is sitting in memory but has never been called and is not usable. It
is in a similar state to the when the system first boots.

Leave the P-SEAMLDR behind. Stop making calls to it. Transition to
calling the new TDX module itself to set up both global and per-cpu
state.

Share tdx_cpu_enable() with the fresh-boot module initialization code.
Export it and invoke it on all CPUs.

Note: "TDX global initialization" needs to be done once before "TDX
per-CPU initialization". It would be a great fit for the new runtime
update "is_lead_cpu" logic. But tdx_cpu_enable() already has some
logic to do the global initialization properly. Just use it directly
to maximize fresh-boot and runtime update code sharing.

== Background ==

The boot-time and post-update initialization flows share the same first
steps:

- TDX global initialization
- TDX per-CPU initialization

After that, they diverge:

- Fresh boot:
   Prepare TDMRs/PAMTs
   Configure the TDX module
   Configure the global KeyID
   Initialize TDMRs
- Runtime update:
   Restore TDX module state from handoff data

Future changes will consume the handoff data.

[ dhansen: major changelog munging ]

Signed-off-by: Chao Gao <chao.gao@intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: Xu Yilun <yilun.xu@linux.intel.com>
Reviewed-by: Tony Lindgren <tony.lindgren@linux.intel.com>
Reviewed-by: Kai Huang <kai.huang@intel.com>
Reviewed-by: Kiryl Shutsemau (Meta) <kas@kernel.org>
Reviewed-by: Rick Edgecombe <rick.p.edgecombe@intel.com>
Link: https://patch.msgid.link/20260520133909.409394-20-chao.gao@intel.com