mtd: afs: rename structs and functions for v1

Since we're gonna add the v2 version of flash information
structure and we want to avoid confusion, rename the old
functions to *v1. Cut the word "structure" from the struct
name, it is pretty obvious that it is a struct already from
the keyword.

Cc: Ryan Harkin <ryan.harkin@linaro.org>
Cc: Liviu Dudau <liviu.dudau@arm.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>
