m68k: defconfig: Update defconfigs for v6.8-rc1

  - Drop CONFIG_MD_LINEAR=m (removed in commit 849d18e2 ("md:
    Remove deprecated CONFIG_MD_LINEAR")),
  - Drop CONFIG_CRYPTO_CFB=m and CONFIG_CRYPTO_OFB=m (removed in commit
    412ac51c ("crypto: cfb,ofb - Remove cfb and ofb")).

Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Link: https://lore.kernel.org/r/902a6cfd5f0c5b67470658dd6dffdd1bac1948b5.1706272008.git.geert@linux-m68k.org