x86: Add a default implementation for cleanup_before_linux()

This function provides an opportunity for some last minute cleanup and
reconfiguration before control is handed over to Linux. It's possible this
may need to do something in the future, but for now it's left empty. It's set
up as a weak symbol so it can be overridden if necessary on a case by case
basis.

Signed-off-by: Gabe Black <gabeblack@chromium.org>
Signed-off-by: Simon Glass <sjg@chromium.org>

arch/x86/cpu/cpu.c

@@ -115,6 +115,11 @@ void setup_gdt(gd_t *id, u64 *gdt_addr)
 	load_fs(X86_GDT_ENTRY_32BIT_FS);
 }
 
+int __weak x86_cleanup_before_linux(void)
+{
+	return 0;
+}
+
 int x86_cpu_init_f(void)
 {
 	const u32 em_rst = ~X86_CR0_EM;

arch/x86/include/asm/u-boot-x86.h

@@ -40,6 +40,7 @@ int cpu_init_f(void);
 void init_gd(gd_t *id, u64 *gdt_addr);
 void setup_gdt(gd_t *id, u64 *gdt_addr);
 int init_cache(void);
+int cleanup_before_linux(void);
 
 /* cpu/.../timer.c */
 void timer_isr(void *);