Add FILE_LICENCE declarations to almost all files that make up the
various standard builds of gPXE.

This is something of an ugly hack to accommodate an OEM requirement.
The NIC has only one expansion ROM BAR, rather than one per port.  To
allow individual ports to be selectively enabled/disabled for PXE boot
(as required), we must therefore leave the expansion ROM always
enabled, and place the per-port enable/disable logic within the gPXE
driver.

The Phantom firmware selectively disables PCI functions based on the
board type, with the end result that we see one PCI function for each
network port.  This allows us to eliminate the code for reading from
flash and, more importantly, removes knowledge of the board type magic
number from the gPXE driver.

This interface provides access to firmware settings (e.g. MAC address)
that will apply to all drivers loaded for the duration of the current
system boot.

A hardware bug means that reads through the expansion ROM BAR can
return corrupted data if the PEGs are running.  This breaks platforms
that re-read the expansion ROM after invoking gPXE code, such as IBM
blade servers.

Halt PEGs during driver shutdown, and unhalt PEGs during driver
startup if we detect that this is not the first startup since
power-on.

Most other Phantom drivers define a register space in terms of a 64M
virtual address space.  While this doesn't map in any meaningful way
to the actual addresses used on the latest cards, it makes maintenance
easier if we do the same.