x86/tdx: Use pg_level in TDX APIs, not the TDX-Module's 0-based level

x86/tdx: Use pg_level in TDX APIs, not the TDX-Module's 0-based level

Rework the TDX APIs to take the kernel's 1-based pg_level enum, not the
TDX-Module's 0-based level.  The APIs are _kernel_ APIs, not TDX-Module
APIs, and the kernel (and KVM) uses "enum pg_level" literally everywhere.

Using "enum pg_level" eliminates ambiguity when looking at the APIs (it's
NOT clear that "int level" refers to the TDX-Module's level), and will
allow for using existing helpers like page_level_size() when support for
hugepages is added to the S-EPT APIs.

No functional change intended.

Cc: Kai Huang <kai.huang@intel.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Rick Edgecombe <rick.p.edgecombe@intel.com>
Cc: Yan Zhao <yan.y.zhao@intel.com>
Cc: Vishal Annapurve <vannapurve@google.com>
Cc: Ackerley Tng <ackerleytng@google.com>
Acked-by: Kiryl Shutsemau <kas@kernel.org>
Reviewed-by: Kai Huang <kai.huang@intel.com>
Tested-by: Kai Huang <kai.huang@intel.com>
Reviewed-by: Rick Edgecombe <rick.p.edgecombe@intel.com>
Tested-by: Rick Edgecombe <rick.p.edgecombe@intel.com>
Acked-by: Dave Hansen <dave.hansen@linux.intel.com>
Link: https://patch.msgid.link/20260129011517.3545883-2-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>