Add UEFI definitions related to converting string to DEVICE_PATH

Add definitions from UEFI 2.7 Errata B standards doc for converting a
text string to a device path. Added clearly missing 'e' at the end of
Device to resolve mismatch in that document in
EFI_DEVICE_PATH_FROM_TEXT_PROTOCOL element names.

Differential Revision: https://reviews.freebsd.org/D19971