usbdebug: Fix reserve in CAR

We need sizeof(struct ehci_dbg_info) of 88 but only
reserved 64 bytes. If usbdebug_hw_init() was called
late in romstage, for some builds it would corrupt
CAR_GLOBALs like console_inited variable and stop
logging anything.

Also change pointer initialisation such that
glob_dbg_info will hit garbage collection for
PRE_RAM stages.

Change-Id: Ib49fca781e55619179aa8888e2d859560e050876
Signed-off-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-on: https://review.coreboot.org/c/31174
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>
Reviewed-by: Nico Huber <nico.h@gmx.de>

src/arch/x86/car.ld

@@ -67,7 +67,8 @@
 	_car_drivers_storage_end = .;
 #endif
 	_car_ehci_dbg_info_start = .;
-        . += 64;
+	/* Reserve sizeof(struct ehci_dbg_info). */
+        . += 88;
         _car_ehci_dbg_info_end = .;
 	/* _car_global_start and _car_global_end provide symbols to per-stage
 	 * variables that are not shared like the timestamp and the pre-ram

src/arch/x86/include/arch/symbols.h

@@ -35,6 +35,9 @@ extern char _car_stack_end[];
 #define _car_stack_size (_car_stack_end - _car_stack_start)
 
 extern char _car_ehci_dbg_info_start[];
+extern char _car_ehci_dbg_info_end[];
+#define _car_ehci_dbg_info_size \
+	(_car_ehci_dbg_info_end - _car_ehci_dbg_info_start)
 
 /*
  * The _car_relocatable_data_[start|end] symbols cover CAR data which is