x86: Provide weak PC/AT compatibility setup function

It is possibly to setup x86 boards to use non-PC/AT configurations. For
example, the sc520 is an x86 CPU with PC/AT and non-PC/AT peripherals.
This function allows the board to set itself up for maximum PC/AT
compatibility just before booting the Linux kernel (the Linux kernel
'just works' if everything is PC/AT compliant)

Signed-off-by: Graeme Russ <graeme.russ@gmail.com>

arch/i386/include/asm/u-boot-i386.h

@@ -43,6 +43,8 @@ int cpu_init_interrupts(void);
 int board_init(void);
 int dram_init(void);
 
+void setup_pcat_compatibility(void);
+
 void isa_unmap_rom(u32 addr);
 u32 isa_map_rom(u32 bus_addr, int size);
 

arch/i386/lib/board.c

@@ -441,3 +441,10 @@ unsigned long do_go_exec (ulong (*entry)(int, char *[]), int argc, char *argv[])
 
 	return (entry) (argc, argv);
 }
+
+void setup_pcat_compatibility(void)
+	__attribute__((weak, alias("__setup_pcat_compatibility")));
+
+void __setup_pcat_compatibility(void)
+{
+}