Merge patch series "pxe: Precursor series for supporting read_all() in extlinux / PXE"

Simon Glass <sjg@chromium.org> says:

This series includes some patches related to allowing read_all() to be
used with the extlinux / PXE bootmeths.

These patches were split out from the stb4 series, since it will need to
have additional patches for LWIP, to avoid breaking PXE booting when
LWIP is used.

Link: https://lore.kernel.org/r/20250306002533.2380866-1-sjg@chromium.org