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

diff --git a/arch/i386/include/asm/u-boot-i386.h b/arch/i386/include/asm/u-boot-i386.h
index 521fd35..ce097a3 100644
--- a/arch/i386/include/asm/u-boot-i386.h
+++ b/arch/i386/include/asm/u-boot-i386.h
@@ -43,6 +43,8 @@
 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

diff --git a/arch/i386/lib/board.c b/arch/i386/lib/board.c
index 7115a2f..3f849f6 100644
--- a/arch/i386/lib/board.c
+++ b/arch/i386/lib/board.c
@@ -441,3 +441,10 @@
 
 	return (entry) (argc, argv);
 }
+
+void setup_pcat_compatibility(void)
+	__attribute__((weak, alias("__setup_pcat_compatibility")));
+
+void __setup_pcat_compatibility(void)
+{
+}