Remove defines pertaining to arbitrary limits not affecting GRUB

	Remove defines pertaining to arbitrary limits not affecting GRUB
	anymore.

	* grub-core/fs/ext2.c (EXT2_PATH_MAX): Removed.
	(EXT2_MAX_SYMLINKCNT): Likewise.
	* grub-core/fs/nilfs2.c (NILFS_BTREE_LEVEL_MAX): Likewise.
	* grub-core/net/tftp.c (TFTP_MAX_PACKET): Likewise.
	* include/grub/i386/pc/pxe.h (GRUB_PXE_MIN_BLKSIZE): Likewise.
	(GRUB_PXE_MAX_BLKSIZE): Likewise.
	* include/grub/normal.h (GRUB_MAX_CMDLINE): Likewise.
	* include/grub/zfs/dnode.h (DN_MAX_INDBLKSHIFT): Likewise.
	(DN_MAX_OBJECT_SHIFT): Likewise.
	(DN_MAX_OFFSET_SHIFT): Likewise.
	(DN_MAX_OBJECT): Likewise.
	(DNODES_PER_LEVEL_SHIFT): Likewise.
	* include/grub/zfs/spa.h (SPA_MAXBLOCKSHIFT): Likewise.
	(SPA_MAXBLOCKSIZE): Likewise.
	(SPA_BLOCKSIZES): Likewise.
	* include/grub/zfs/zap_impl.h (MZAP_MAX_BLKSHIFT): Likewise.
	(MZAP_MAX_BLKSZ): Likewise.