scripts/analyse-9p-simpletrace.py: Add symbolic names for 9p operations.

scripts/analyse-9p-simpletrace.py:	Add symbolic names for 9p operations.

Currently, we just print the numerical value of 9p operation identifier in
case of RERROR which is less meaningful for readability. Mapping 9p
operation ids to symbolic names provides a better tracelog:

	RERROR (tag = 1 , id = TWALK , err = " No such file or directory ")
	RERROR (tag = 1 , id = TUNLINKAT , err = " Directory not empty ")

This patch provides a dictionary of all possible 9p operation symbols mapped
to their numerical identifiers which are likely to be used in future at
various places in this script.

Signed-off-by: Harsh Prateek Bora <harsh@linux.vnet.ibm.com>
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>