[USN-3531-3] intel-microcode update

Software Description:
- intel-microcode: Processor microcode for Intel CPUs

Details:
Jann Horn discovered that microprocessors utilizing speculative execution
and branch prediction may allow unauthorized memory reads via sidechannel
attacks. This flaw is known as Spectre. A local attacker could use this to
expose sensitive information, including kernel memory. (CVE-2017-5715)

This update provides the corrected microcode updates required for the
corresponding Linux kernel updates.

References:
  https://usn.ubuntu.com/usn/usn-3531-3
  https://usn.ubuntu.com/usn/usn-3531-1
  CVE-2017-5715