x86/virt/tdx: Move TDX_FEATURES0 bits to asm/tdx.h

x86/virt/tdx: Move TDX_FEATURES0 bits to asm/tdx.h

Future changes will add support for new TDX features exposed as
TDX_FEATURES0 bits. The presence of these features will need to be
checked outside of arch/x86/virt. The feature query helpers and
the TDX_FEATURES0 defines they reference will need to live in the
widely accessible asm/tdx.h header. Move the existing TDX_FEATURES0 to
asm/tdx.h so that they can all be kept together.

Opportunistically switch to BIT_ULL() since TDX_FEATURES0 is 64-bit.

No functional change intended.

[ dhansen: grammar fixups ]

Signed-off-by: Chao Gao <chao.gao@intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Link: https://lore.kernel.org/kvm/20260427152854.101171-17-chao.gao@intel.com/
Link: https://lore.kernel.org/kvm/20251121005125.417831-16-rick.p.edgecombe@intel.com/
Link: https://patch.msgid.link/20260520133909.409394-5-chao.gao@intel.com