elog-gen.py : read multiple error yaml files

This change enables the elog-gen script to look at more than one error
yaml file (and corresponding metadata yaml file). The input to the
script had to be changed to a yaml directory, containing
error yaml files, instead of a single error yaml file.

The reason to support reading multiple error yaml files is that,
without this, applications have to all dump their errors in a single big
error yaml file. Now it's possible to write application/domain specific
error yaml files; they just need to be exported to the same location,
from where elog-gen.py can pick them.

Change-Id: I9418bf0e0b54a7b7f7701b337649cb8eb4c54913
Signed-off-by: Deepak Kodihalli <dkodihal@in.ibm.com>
diff --git a/tools/example/xyz/openbmc_project/Example/Foo.errors.yaml b/tools/example/xyz/openbmc_project/Example/Foo.errors.yaml
new file mode 100644
index 0000000..73fe62b
--- /dev/null
+++ b/tools/example/xyz/openbmc_project/Example/Foo.errors.yaml
@@ -0,0 +1,2 @@
+- name: Foo
+  description: this is test error Foo