Sometimes we want to read/write more than 4 bytes of chip content at once

Add chip_{read,write}n to the external flasher infrastructure which
read/write n bytes at once.

Fix a few places where the code used memcpy/memcmp although that is
strictly impossible with external flashers.
Place a FIXME in the layout.c code because usage is not totally clear
and needs to be fixed to support external flashers.

As a nice side benefit, we get a noticeable speedup for builtin flash
reading which is now a memcpy() of the full flash area instead of a
series of single-byte reads.

Corresponding to flashrom svn r579.

Signed-off-by: Carl-Daniel Hailfinger <c-d.hailfinger.devel.2006@gmx.net>
Acked-by: Urja Rannikko <urjaman@gmail.com>
Acked-by: Uwe Hermann <uwe@hermann-uwe.de>

layout.c

@@ -220,6 +220,7 @@ int handle_romentries(uint8_t *buffer, uint8_t *content)
 		if (rom_entries[i].included)
 			continue;
 
+	/* FIXME: Adapt to the external flasher infrastructure. */
 		memcpy(buffer + rom_entries[i].start,
 		       content + rom_entries[i].start,
 		       rom_entries[i].end - rom_entries[i].start);