Update Storwize/SVC driver documentation.

This update reflects changes made to the Storwize/SVC driver for the
Icehouse release.

Adding Storwize/SVC driver support volume retype.

Change-Id: I53cd5d3df2e751d2754d6d14d4869f12c282155b
s/addding/adding/g

This seems to have been copy & pasted as comment.

Change-Id: Ife6638857b3bc155e3da3389c8ddef2b2ee52c35
Merge "Update Storwize/SVC driver documentation."