arch/arm: Pass cbmem_top to ramstage via calling argument

This solution is very generic and can in principle be implemented on
all arch/soc.

Instead trying to figure out which files can be removed from stages
and which cbmem_top implementations need with preprocessor, rename all
cbmem_top implementation to cbmem_top_romstage.

Mechanisms set in place to pass on information from rom- to ram-stage
will be placed in a followup commit.

Change-Id: If31f0f1de17ffc92c9397f32b26db25aff4b7cab
Signed-off-by: Arthur Heymans <arthur@aheymans.xyz>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/36145
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-by: Julius Werner <jwerner@chromium.org>

src/arch/arm/Kconfig

@@ -17,6 +17,7 @@ config ARCH_ROMSTAGE_ARM
 config ARCH_RAMSTAGE_ARM
 	bool
 	select ARCH_ARM
+	select RAMSTAGE_CBMEM_TOP_ARG
 
 source src/arch/arm/armv4/Kconfig
 source src/arch/arm/armv7/Kconfig

src/arch/arm/include/arch/stages.h

@@ -14,8 +14,9 @@
 #ifndef __ARCH_STAGES_H
 #define __ARCH_STAGES_H
 
+#include <stdint.h>
 #include <main_decl.h>
 
-void stage_entry(void);
+void stage_entry(uintptr_t stage_arg);
 
 #endif

src/arch/arm/stages.c

@@ -22,13 +22,16 @@
  * .text.stage_entry section created by -ffunction-sections).
  */
 
+#include <cbmem.h>
 #include <arch/stages.h>
 #include <arch/cache.h>
 
 /**
  * generic stage entry point. override this if board specific code is needed.
  */
-__weak void stage_entry(void)
+__weak void stage_entry(uintptr_t stage_arg)
 {
+	if (!ENV_ROMSTAGE_OR_BEFORE)
+		_cbmem_top_ptr = stage_arg;
 	main();
 }