sof-tplgreader.py: add warning the tool is about PCMs, not pipelines

Too much confusion all over the place to perform a mass search/replace
so add a warning only at the top of the "help" text.

Signed-off-by: Marc Herbert <marc.herbert@intel.com>

Author: marc-hb

tools/sof-tplgreader.py

@@ -304,7 +304,7 @@ def parse_and_set_block_keyword(block_str, tplgreader):
 
     import argparse
 
-    parser = argparse.ArgumentParser(description='Warp Tools to mapping tplgreader convert TPLG file.',
+    parser = argparse.ArgumentParser(description='Filters and prints PCMs found in a .tplg file',
         add_help=True, formatter_class=argparse.RawTextHelpFormatter)
 
     parser.add_argument('filename', type=str, help='tplg file name, multi-tplg file name use "," to split it')
@@ -315,7 +315,7 @@ def parse_and_set_block_keyword(block_str, tplgreader):
 string support & | and ~ logic operation.
 if only care about key, you can use 'key':'any'.
 
-NOTE: pipelines are filtered according to their key-value attributes pairs,
+NOTE: pipelines (actually: _PCMs_) are filtered according to their key-value attributes pairs,
 the value in a key-value pair is either numerical or non-numerical. Strings
 contain only digits are considered numerical, and others are considered
 non-numerical. Exact value match will be carried out for numerical values,