rename try_make_readable() to try_make_writable()

In practice this function makes things readable and writable,
so use a less confusing name.

Test: TreeHugger, 'git grep try_make_readable' comes up empty
Signed-off-by: Maciej Żenczykowski <maze@google.com>
Change-Id: I32faad148cc5714cf0ec7246620376ed4dd3d6d2