PEL: Usability fixes to msg registry validator

This commit makes some usability improvements to the script that
validates the PEL message registry.

1) Renames the script from process_registry.py to validate_registry.py
   to more accurately reflect what it does.
2) Removes the '-v' option that was required to make it do any
   validation and just run it by default.  (At one point in the past it
   was going to do more than just validation.)

An internal improvement was made to just use argparse's ability to
check for required parameters instead of checking manually.

Signed-off-by: Matt Spinler <spinler@us.ibm.com>
Change-Id: I30c4ba5c693388048095b385d5cae1993e906975
diff --git a/extensions/openpower-pels/registry/run-ci.sh b/extensions/openpower-pels/registry/run-ci.sh
index 277b12e..023d22c 100755
--- a/extensions/openpower-pels/registry/run-ci.sh
+++ b/extensions/openpower-pels/registry/run-ci.sh
@@ -1,4 +1,4 @@
 #!/bin/sh
-/usr/bin/env python3 extensions/openpower-pels/registry/tools/process_registry.py \
-    -v -s extensions/openpower-pels/registry/schema/schema.json \
+/usr/bin/env python3 extensions/openpower-pels/registry/tools/validate_registry.py \
+    -s extensions/openpower-pels/registry/schema/schema.json \
     -r extensions/openpower-pels/registry/message_registry.json