CBMEM: Always select CAR_MIGRATION

If romstage does not make cbmem_initialize() call, linker should
optimize the code for CAR migration away.

This simplifies design of CBMEM console by a considerable amount.
As console buffer is now migrated within cbmem_initialize() call there
is no longer need for cbmemc_reinit() call made at end of romstage.

Change-Id: I8675ecaafb641fa02675e9ba3f374caa8e240f1d
Signed-off-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-on: http://review.coreboot.org/3916
Tested-by: build bot (Jenkins)
Reviewed-by: Aaron Durbin <adurbin@google.com>

src/arch/x86/boot/cbmem.c

@@ -47,7 +47,7 @@ void __attribute__((weak)) backup_top_of_ram(uint64_t ramtop)
 
 /* This is for compatibility with old boards only. Any new chipset and board
  * must implement get_top_of_ram() for both romstage and ramstage to support
- * features like CAR_MIGRATION and CBMEM_CONSOLE.
+ * early features like COLLECT_TIMESTAMPS and CBMEM_CONSOLE.
  */
 void set_top_of_ram(uint64_t ramtop)
 {