Header rearrangement.

I want to get to the point where any header in include/ reflects a
standard user-level header (e.g. a POSIX header), while everything that's
specific to gPXE lives in include/gpxe/.  Headers that reflect a Linux
header (e.g. if_ether.h) should also be in include/gpxe/, with the same
name as the Linux header and, preferably, the same names used for the
definitions.

src/drivers/net/etherfabric.c

@@ -18,7 +18,7 @@
 
 #include "etherboot.h"
 #include "nic.h"
-#include "pci.h"
+#include <gpxe/pci.h>
 #include "timer.h"
 #define dma_addr_t unsigned long
 #include "etherfabric.h"