Merge patch series "boot: fix crash in bootflow menu with EFI BOOTMGR support + typos"

Quentin Schulz <foss+uboot@0leil.net> says:

bootflow menu currently crashes U-Boot with a NULL pointer dereference
because bootflow->dev is NULL for global bootmeths (such as EFI BOOTMGR).
Therefore, let's check if the bootflow is associated with a global
bootmeth before trying to make it part of the menu.

While this makes U-Boot not crash anymore, bootflow menu doesn't work
for me (I have never had a happy path with it, but I haven't actually
tried it before today :) ) and this was basically just implemented
following Simon's suggestion sent over IRC. No clue if this is enough or
just a quick band-aid patch.

This also fixes typos in multiple places.