Merge patch series "membuff: Add tests and update to support a flag for empty/full"

Simon Glass <sjg@chromium.org> says:

The membuff implementation curently has no tests. It also assumes that
head and tail can never correspond unless the buffer is empty.

This series provides a compile-time flag to support a 'full' flag. It
also adds some tests of the main routines.

The data structure is also renamed to membuf which fits better with
U-Boot.

There may be some cases in the code which could be optimised a little,
but the implementation is functional.

Link: https://lore.kernel.org/r/20250318152059.1464369-1-sjg@chromium.org