[CLASS][GRUB-EFI] Extend `grub-efi-cfg` class
Extend poky's grub-efi-cfg
class to allow initrds in GRUB's boot
configuration. This GRUB configuration is the one that is installed into
the board after the install procedure with removable media.
JIRA Reference: [CLEAOS-616]
Signed-off-by: Nicola Sparnacci nicola.sparnacci@seco.com