[legal] Add a selection of FILE_LICENCE declarations

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

src/arch/i386/firmware/pcbios/basemem.c

@@ -16,6 +16,8 @@
  * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  */
 
+FILE_LICENCE ( GPL2_OR_LATER );
+
 #include <stdint.h>
 #include <realmode.h>
 #include <bios.h>

src/arch/i386/firmware/pcbios/bios_console.c

@@ -16,6 +16,8 @@
  * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  */
 
+FILE_LICENCE ( GPL2_OR_LATER );
+
 #include <assert.h>
 #include <realmode.h>
 #include <console.h>

src/arch/i386/firmware/pcbios/e820mangler.S

@@ -15,7 +15,9 @@
  * along with this program; if not, write to the Free Software
  * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  */
-	
+
+FILE_LICENCE ( GPL2_OR_LATER )
+
 	.text
 	.arch i386
 	.code16

src/arch/i386/firmware/pcbios/fakee820.c

@@ -15,6 +15,8 @@
  * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  */
 
+FILE_LICENCE ( GPL2_OR_LATER );
+
 #include <realmode.h>
 #include <biosint.h>
 

src/arch/i386/firmware/pcbios/gateA20.c

@@ -1,3 +1,5 @@
+FILE_LICENCE ( GPL2_OR_LATER );
+
 #include <stdio.h>
 #include <realmode.h>
 #include <bios.h>

src/arch/i386/firmware/pcbios/hidemem.c

@@ -15,6 +15,8 @@
  * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  */
 
+FILE_LICENCE ( GPL2_OR_LATER );
+
 #include <assert.h>
 #include <realmode.h>
 #include <biosint.h>

src/arch/i386/firmware/pcbios/memmap.c

@@ -16,6 +16,8 @@
  * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  */
 
+FILE_LICENCE ( GPL2_OR_LATER );
+
 #include <stdint.h>
 #include <errno.h>
 #include <realmode.h>

src/arch/i386/firmware/pcbios/pnpbios.c

@@ -16,6 +16,8 @@
  * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  */
 
+FILE_LICENCE ( GPL2_OR_LATER );
+
 #include <stdint.h>
 #include <string.h>
 #include <errno.h>