x86/sgx: Document structs and enums with '@', not '%'

x86/sgx: Document structs and enums with '@', not '%'

Use '@' to document structure members and enum values in kernel-doc markup,
as per Documentation/doc-guide/kernel-doc.rst and flagged by make htmldocs.

  WARNING: arch/x86/include/uapi/asm/sgx.h:17 Enum value 'SGX_PAGE_MEASURE'
           not described in enum 'sgx_page_flags'

Opportunistically add a missing ':' for SGX_CHILD_PRESENT.

Closes: https://lore.kernel.org/all/20251106145506.145fc620@canb.auug.org.au
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: Kai Huang <kai.huang@intel.com>
Link: https://patch.msgid.link/20251112160708.1343355-4-seanjc%40google.com