intel-microcode: bump to version 20180807a

The big "intel-microcode.dat" text file is gone. Only binary files are
provided, in the "intel-ucode" directory. Install it at /lib/firmware/,
like linux-firmware does, and update the iucode-tool init script to use
that path.

We don't install the microcode under "intel-ucode-with-caveats", since
it needs special commits in the Linux kernel (see "relnotes" for more
information).

Tested on an equipment with Intel C3000 processor.

Signed-off-by: Carlos Santos <casantos@datacom.com.br>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>