* grub-core/kern/ieee1275/ieee1275.c (grub_ieee1275_write): Make buffer
	const void *.
	* include/grub/ieee1275/ieee1275.h (grub_ieee1275_write): Likewise.
	* grub-core/disk/ieee1275/ofdisk.c (grub_ofdisk_read): Move open
	and seek loginc to ...
	(grub_ofdisk_prepare): ... here.
	(grub_ofdisk_write): Implement.