timestamps: Remove TIMESTAMP_CACHE_IN_BSS

This was implemented for LATE_CBMEM_INIT support which
has already been deprecated.

Change-Id: I39225ba675bc3389e051e15b400a905431969715
Signed-off-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/35375
Reviewed-by: Furquan Shaikh <furquan@google.com>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/arch/x86/postcar.c

@@ -31,7 +31,10 @@ void main(void)
 
 	console_init();
 
-	/* Recover cbmem so infrastruture using it is functional. */
+	/*
+	 * CBMEM needs to be recovered because timestamps rely on
+	 * the cbmem infrastructure being around. Explicitly recover it.
+	 */
 	cbmem_initialize();
 
 	timestamp_add_now(TS_START_POSTCAR);