Unify ID_SECTION_OFFSET and mark it deprecated

We used to put the id section at -0x10, with some boards overriding
this to avoid collisions with romstraps.
Hardcode the location at -0x80, at the possible expense of some space
(0x70 bytes).
This also makes the section easier to find in a binary image.

At some point, CONFIG_ID_SECTION_OFFSET can be removed, so this option
is moved to src/Kconfig.deprecated_options.

Change-Id: I6ce2d6e94e57717939bda070bfe0c9df80ca2a89
Signed-off-by: Patrick Georgi <patrick.georgi@secunet.com>
Reviewed-on: http://review.coreboot.org/549
Tested-by: build bot (Jenkins)
Reviewed-by: Peter Stuge <peter@stuge.se>

src/southbridge/nvidia/ck804/Kconfig

@@ -10,10 +10,6 @@ config BOOTBLOCK_SOUTHBRIDGE_INIT
 	string
 	default "southbridge/nvidia/ck804/bootblock.c"
 
-config ID_SECTION_OFFSET
-	hex
-	default 0x80
-
 config EHCI_BAR
 	hex
 	default 0xfef00000

src/southbridge/nvidia/mcp55/Kconfig

@@ -9,10 +9,6 @@ config BOOTBLOCK_SOUTHBRIDGE_INIT
 	string
 	default "southbridge/nvidia/mcp55/bootblock.c"
 
-config ID_SECTION_OFFSET
-	hex
-	default 0x80
-
 config EHCI_BAR
 	hex
 	default 0xfef00000

src/southbridge/sis/sis966/Kconfig

@@ -7,10 +7,6 @@ config BOOTBLOCK_SOUTHBRIDGE_INIT
 	string
 	default "southbridge/sis/sis966/bootblock.c" if SOUTHBRIDGE_SIS_SIS966
 
-config ID_SECTION_OFFSET
-	hex
-	default 0x80 if SOUTHBRIDGE_SIS_SIS966
-
 config EHCI_BAR
 	hex
 	default 0xfef00000 if SOUTHBRIDGE_SIS_SIS966

src/southbridge/via/k8t890/Kconfig

@@ -50,7 +50,3 @@ config VIDEO_MB
 	default -1  if K8M890_VIDEO_MB_CMOS
 	depends on SOUTHBRIDGE_VIA_K8M890_VGA_EN
 
-config ID_SECTION_OFFSET
-	hex
-	default 0x80 if SOUTHBRIDGE_VIA_K8M800 || SOUTHBRIDGE_VIA_K8T800_OLD || SOUTHBRIDGE_VIA_K8T800 || SOUTHBRIDGE_VIA_K8T800PRO || SOUTHBRIDGE_VIA_K8M890 || SOUTHBRIDGE_VIA_K8T890
-