[U-Boot] [x86] use gc sections to reduce image size

[Graeme Russ <graeme.russ@gmail.com>]

I have run a quick test on x86 with a saving of 5.8kB with no apparent
problems. NOTE: If I add -fdata-sections as per the NIOS patches, U-Boot
fails to run.

I'm in the middle of a major re-write of the x86 startup code and will
include this as a formal patch when that work is complete.

Regards,

Graeme

diff --git a/arch/i386/config.mk b/arch/i386/config.mk
index 4b990e0..0e80a1a 100644
--- a/arch/i386/config.mk
+++ b/arch/i386/config.mk
@@ -26,3 +26,6 @@ CROSS_COMPILE ?= i386-linux-
 STANDALONE_LOAD_ADDR = 0x40000

 PLATFORM_CPPFLAGS += -DCONFIG_I386 -D__I386__
+
+LDFLAGS += --cref --gc-sections
+PLATFORM_RELFLAGS += -ffunction-sections
diff --git a/board/eNET/u-boot.lds b/board/eNET/u-boot.lds
index d78d75f..7b211a8 100644
--- a/board/eNET/u-boot.lds
+++ b/board/eNET/u-boot.lds
@@ -77,13 +77,13 @@ SECTIONS
 	_i386boot_bss_size = SIZEOF(.bss);

 	/* 16bit realmode trampoline code */
-	.realmode 0x7c0 : AT ( LOADADDR(.rel.dyn) + SIZEOF(.rel.dyn) ) {
*(.realmode) }
+	.realmode 0x7c0 : AT ( LOADADDR(.rel.dyn) + SIZEOF(.rel.dyn) ) {
KEEP(*(.realmode)) }

 	_i386boot_realmode = LOADADDR(.realmode);
 	_i386boot_realmode_size = SIZEOF(.realmode);

 	/* 16bit BIOS emulation code (just enough to boot Linux) */
-	.bios 0 : AT ( LOADADDR(.realmode) + SIZEOF(.realmode) ) { *(.bios) }
+	.bios 0 : AT ( LOADADDR(.realmode) + SIZEOF(.realmode) ) { KEEP(*(.bios)) }

 	_i386boot_bios = LOADADDR(.bios);
 	_i386boot_bios_size = SIZEOF(.bios);
@@ -98,12 +98,12 @@ SECTIONS
 	 * The fff0 offset of resetvec is important, however.
 	 */
 	. = 0xfffffe00;
-	.start32 : AT (TEXT_BASE + 0x3fe00) { *(.start32); }
+	.start32 : AT (TEXT_BASE + 0x3fe00) { KEEP(*(.start32)); }

 	. = 0xf800;
-	.start16 : AT (TEXT_BASE + 0x3f800) { *(.start16); }
+	.start16 : AT (TEXT_BASE + 0x3f800) { KEEP(*(.start16)); }

 	. = 0xfff0;
-	.resetvec : AT (TEXT_BASE + 0x3fff0) { *(.resetvec); }
+	.resetvec : AT (TEXT_BASE + 0x3fff0) { KEEP(*(.resetvec)); }
 	_i386boot_end = (LOADADDR(.resetvec) + SIZEOF(.resetvec) );
 }