[PATCH AUTOSEL for 4.9 223/293] tools lib traceevent: Fix get_field_str() for dynamic strings

From: "Steven Rostedt (VMware)" [ Upstream commit d777f8de99b05d399c0e4e51cdce016f26bd971b ] If a field is a dynamic string, get_field_str() returned just the offset/size value and not the string. Have it parse the offset/size correctly to return the actual string.

[PATCH AUTOSEL for 4.9 223/293] tools lib traceevent: Fix get_field_str() for dynamic strings

From: "Steven Rostedt (VMware)" [ Upstream commit d777f8de99b05d399c0e4e51cdce016f26bd971b ] If a field is a dynamic string, get_field_str() returned just the offset/size value and not the string. Have it parse the offset/size correctly to return the actual string. Otherwise filtering fails