intel/dev: Bail when INTEL_DEVID_OVERRIDE is not valid
Avoids surprises where you set an OVERRIDE but it gets ignored and the system PCI ID is used.
Also fixes the bug that the error of invalid platform name being printed too early, even when the passed platform was a PCI ID (which is also supported).
For the case where euid != uid, a warning was added but the behavior wasn't changed: it is still going to fallback to system PCI ID.