OvmfPkg/OvmfPkg.ci.yaml: Add configuration for LicenseCheck

Add configuration IgnoreFiles for package config files.
So users can rely on this to skip license conflict for
some generated files.

Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Laszlo Ersek <lersek@redhat.com>
Cc: Ard Biesheuvel <ard.biesheuvel@arm.com>
Signed-off-by: Shenglei Zhang <shenglei.zhang@intel.com>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>