KVM: TDX: Derive error argument names from the local variable names

KVM: TDX: Derive error argument names from the local variable names

When printing SEAMCALL errors, use the name of the variable holding an
error parameter instead of the register from whence it came, so that flows
which use descriptive variable names will similarly print descriptive
error messages.

Suggested-by: Rick Edgecombe <rick.p.edgecombe@intel.com>
Reviewed-by: Binbin Wu <binbin.wu@linux.intel.com>
Reviewed-by: Yan Zhao <yan.y.zhao@intel.com>
Tested-by: Yan Zhao <yan.y.zhao@intel.com>
Tested-by: Kai Huang <kai.huang@intel.com>
Link: https://patch.msgid.link/20251030200951.3402865-20-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>