dracut: Do not create early_cpio if no suitable microcode exist in hostonly case

dracut: Do not create early_cpio if no suitable microcode exist in hostonly case

Intel microcodes only exist for very specific family/model/stepping CPUs.
If no microcode gets added, there is no need to create an empty
(only directories) cpio later that gets glued to the initrd.

This also fixes:

*** Constructing GenuineIntel.bin ****
cat: /lib/firmware/intel-ucode/06-3c-03: No such file or directory

in hostonly mode if there is no suitable microcode for the CPU.

Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: Thomas Renninger <trenn@suse.de>