Added a description

[ROCm/rocminfo commit: ac08c20724]

projects/rocminfo/docs/how-to/use-rocm-agent-enumerator.rst

@@ -6,6 +6,8 @@
 Using ROCm agent enumerator
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+While ROCmInfo gives information about the HSA system attributes and agents, "rocm_agent_enumerator" prints the list of available AMD GCN ISA or architecture names. With the option '-name', it prints out available architectures names obtained from ROCmInfo.
+
 The following products support ROCmInfo:
 
 - gfx000