[ESIMD] Fix documentation issue related to incorrect presentation of namespaces using macros as names (#6197)

Author: fineg74

sycl/doc/doxygen.cfg.in

@@ -2106,7 +2106,9 @@ INCLUDE_FILE_PATTERNS  =
 
 PREDEFINED             = "__SYCL_INLINE_NAMESPACE(X)=namespace X" \
                          "__SYCL_EXPORT" \
-                         "__SYCL_EXPORT_DEPRECATED(x)="
+                         "__SYCL_EXPORT_DEPRECATED(x)=" \
+                         "__ESIMD_NS=sycl::ext::intel::esimd" \
+                         "__ESIMD_ENS=sycl::ext::intel::experimental::esimd"
 
 # If the MACRO_EXPANSION and EXPAND_ONLY_PREDEF tags are set to YES then this
 # tag can be used to specify a list of macro names that should be expanded. The