CBMEM console: Fix and enhance pre-RAM support

Use the value of CONSOLE_PRERAM_BUFFER_SIZE to determine if we can
do CBMEM console in bootblock and romstage. Kconfig forces it to zero
if _BASE is unset or we cannot do CAR migration on x86.

Add CBMEM console to bootblock, except for x86. Only one of bootblock
and romstage clears the pre-RAM buffer.

To start with empty console log on S3 wakeup, ramstage now clears
previous contents of CBMEM buffer if there was no pre-RAM buffer.

Unify Kconfig variable naming.

TODO: ARM configurations do not define PRERAM_BUFFER_BASE values.

Change-Id: I70d82da629529dbfd7bc9491223abd703cbc0115
Signed-off-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-on: http://review.coreboot.org/7862
Tested-by: build bot (Jenkins)
Reviewed-by: Aaron Durbin <adurbin@google.com>

src/console/Kconfig

@@ -175,8 +175,9 @@ config CONSOLE_CBMEM
 	  Enable this to save the console output in a CBMEM buffer. This would
 	  allow to see coreboot console output from Linux space.
 
+if CONSOLE_CBMEM
+
 config CONSOLE_CBMEM_BUFFER_SIZE
-	depends on CONSOLE_CBMEM
 	hex "Room allocated for console output in CBMEM"
 	default 0x20000
 	help
@@ -184,9 +185,14 @@ config CONSOLE_CBMEM_BUFFER_SIZE
 	  value (128K or 0x20000 bytes) is large enough to accommodate
 	  even the BIOS_SPEW level.
 
+config CONSOLE_PRERAM_BUFFER_BASE
+	hex
+	default 0xabadbeef if !CACHE_AS_RAM || BROKEN_CAR_MIGRATE
+	default 0x0
+
 config CONSOLE_PRERAM_BUFFER_SIZE
-	depends on CONSOLE_CBMEM
-	hex "Room allocated for console output before RAM is initialized"
+	hex
+	default 0x0 if CONSOLE_PRERAM_BUFFER_BASE = 0xabadbeef
 	default 0xc00
 	help
 	  Console is used before RAM is initialized. This is the room reserved
@@ -194,6 +200,8 @@ config CONSOLE_PRERAM_BUFFER_SIZE
 	  can be saved in a CBMEM buffer. 3K bytes should be enough even for
 	  the BIOS_SPEW level.
 
+endif
+
 config CONSOLE_QEMU_DEBUGCON
 	bool "QEMU debug console output"
 	depends on BOARD_EMULATION_QEMU_X86