runqemu: Add support to handle EnrollDefaultKeys PK/KEK1 certificate

runqemu: Add support to handle EnrollDefaultKeys PK/KEK1 certificate

The EnrollDefaultKeys.efi application (distributed in ovmf-shell-image)
expects the hypervisor to provide a Platform Key and first Key Exchange
Key certificate.

For QEMU, this is done by adding an OEM string in the Type 11 SMBIOS
table. The string contains the EnrollDefaultKeys application GUID followed
by the certificate string. For now, the string is passed in the command
line until QEMU understands OEM strings from regular files (please see
https://bugs.launchpad.net/qemu/+bug/1826200).

If runqemu detects it is given an OVMF binary with support for Secure Boot
(i.e., ovmf.secboot* binaries), extract the certificate string from the
OvmfPkKek1.pem certificate and modify the command-line parameters to
provide the key. Such certificate is created when building OVMF with
support for Secure Boot.

Cc: Ross Burton <ross.burton@intel.com>
Cc: Patrick Ohly <patrick.ohly@intel.com>
(From OE-Core rev: 5e47316ae62f7632fb62bc3b8093ac42f9e3541c)

Signed-off-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>