rmodule: add ramstage support

Coreboot's ramstage defines certain sections/symbols in its fixed
static linker script. It uses these sections/symbols for locating the
drivers as well as its own program information.  Add these sections
and symbols to the rmodule linker script so that ramstage can be
linked as an rmodule. These sections and symbols are a noop for other
rmodule-linked programs, but they are vital to the ramstage.

Also add a comment in coreboot_ram.ld to mirror any changes made there
to the rmodule linker script.

Change-Id: Ib9885a00e987aef0ee1ae34f1d73066e15bca9b1
Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: http://review.coreboot.org/2786
Tested-by: build bot (Jenkins)
Reviewed-by: Marc Jones <marc.jones@se-eng.com>

src/arch/x86/coreboot_ram.ld

@@ -50,6 +50,10 @@ SECTIONS
 	.rodata : {
 		_rodata = .;
 		. = ALIGN(4);
+
+		/* If any changes are made to the driver start/symbols or the
+		 * section names the equivalent changes need to made to
+		 * rmodule.ld. */
 		console_drivers = .;
 		*(.rodata.console_drivers)
 		econsole_drivers = . ;
@@ -60,6 +64,7 @@ SECTIONS
 		cpu_drivers = . ;
 		*(.rodata.cpu_driver)
 		ecpu_drivers = . ;
+
 		*(.rodata)
 		*(.rodata.*)
 		/* kevinh/Ispiri - Added an align, because the objcopy tool