Unlike linked lists, it is inefficient to remove items from an alist,
particularly if it is large. If most items need to be removed, then the
time-complexity approaches O(n2).

Provide a way to do this efficiently, by working through the alist once
and copying elements down.

Signed-off-by: Simon Glass <sjg@chromium.org>

Sometimes it is useful to empty the list without de-allocating any of
the memory used, e.g. when the list will be re-populated immediately
afterwards.

Add a new function for this.

Signed-off-by: Simon Glass <sjg@chromium.org>

Add some macros which permit easy iteration through an alist, similar to
those provided by the 'list' implementation.

Signed-off-by: Simon Glass <sjg@chromium.org>

Add a new function which returns the next element after the one
provided, if it exists in the list.

Signed-off-by: Simon Glass <sjg@chromium.org>

In various places it is useful to have an array of structures, but allow
it to grow. In some cases we work around it by setting maximum number of
entries, using a Kconfig option. In other places we use a linked list,
which does not provide for random access and can complicate the code.

Introduce a new data structure, which is a variable-sized list of structs
each of the same, pre-set size. It provides O(1) access and is reasonably
efficient at expanding linearly, since it doubles in size when it runs out
of space.

Signed-off-by: Simon Glass <sjg@chromium.org>