microcode_ctl security, bug fix and enhancement update

[4:20210216-1.20210608.0.1]

• add support for UEK6 kernels
• enable early update for 06-4f-01
• remove no longer appropriate caveats for 06-2d-07 and 06-55-04
• enable early and late load on RHCK
  [4:20210216-1.20210608.1]
• Update Intel CPU microcode to microcode-20210608 release:
  • Fixes in releasenote.md file.
    [4:20210216-1.20210525.2]
• Make intel-06-2d-07, intel-06-4e-03, intel-06-4f-01, intel-06-55-04,
  intel-06-5e-03, intel-06-8c-01, intel-06-8e-9e-0x-0xca,
  and intel-06-8e-9e-0x-dell caveats dependent on intel caveat.
• Enable 06-8c-01 microcode update by default (#1972328).
• Enable 06-5e-03 microcode update by default (#1972325).