linux-*: enable NLS_ASCII for kernels that support EFI boot
These kernels must have NLS_ASCII set after bb6d7a05, or else they cannot mount the ESP as /boot and boot fails. This kconfig option will be added to the pmb efi kconfig check so that this is caught in the future pre-merge.
FYI I considered reverting those two commits until these kconfig updates were merged, but reverting 3909b1db is especially difficult since it's modifying fstab in a post-install script.. the revert would be very messy (sed to remove the iocharset from a patched fstab, then a patch later to re-add it, or something. didn't seem worth doing)
Edited by clayton craft