We know that with some firmware implementations writing too much data to
UEFI variables can lead to bricking machines. Recent changes attempt to
address this issue, but for some it may still be prudent to avoid
writing large amounts of data until the solution has been proven on a
wide variety of hardware.
Crash dumps or other data from pstore can potentially be a large data
source. Add a new option, CONFIG_EFI_VARS_PSTORE, which can be set to N
to avoid using efivars as a backend to pstore.