x86: add more boot protocol documentation

Signed-off-by: Ian Campbell <ijc@hellion.org.uk>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Jeremy Fitzhardinge <jeremy@goop.org>
Acked-by: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

Documentation/i386/boot.txt

@@ -40,9 +40,17 @@ Protocol 2.05:	(Kernel 2.6.20) Make protected mode kernel relocatable.
 		Introduce relocatable_kernel and kernel_alignment fields.
 
 Protocol 2.06:	(Kernel 2.6.22) Added a field that contains the size of
-		the boot command line
+		the boot command line.
 
-Protocol 2.09:	(kernel 2.6.26) Added a field of 64-bit physical
+Protocol 2.07:	(Kernel 2.6.24) Added paravirtualised boot protocol.
+		Introduced hardware_subarch and hardware_subarch_data
+		and KEEP_SEGMENTS flag in load_flags.
+
+Protocol 2.08:	(Kernel 2.6.26) Added crc32 checksum and ELF format
+		payload. Introduced payload_offset and payload length
+		fields to aid in locating the payload.
+
+Protocol 2.09:	(Kernel 2.6.26) Added a field of 64-bit physical
 		pointer to single linked list of struct	setup_data.
 
 **** MEMORY LAYOUT