U-Boot: Fix linking the kernel by adding FDT support

Add FDT support to the kernel,
move fdt_support.cpp and declare gFDT there for the kernel.

src/system/boot/platform/u-boot/Jamfile

@@ -248,7 +248,7 @@ Depends haiku-mmc-image : haiku-$(HAIKU_BOOT_BOARD).mmc ;
 SEARCH on [ FGristFiles $(genericPlatformSources) ]
 	= [ FDirName $(HAIKU_TOP) src system boot platform generic ] ;
 
-SEARCH on [ FGristFiles openfirmware.cpp ]
+SEARCH on [ FGristFiles openfirmware.cpp fdt_support.cpp ]
 	= [ FDirName $(HAIKU_TOP) src system kernel platform u-boot ] ;
 
 SEARCH on [ FGristFiles $(libFDTSources) ]

src/system/kernel/platform/u-boot/Jamfile

@@ -5,7 +5,22 @@ SubDirC++Flags $(TARGET_KERNEL_PIC_CCFLAGS) ;
 
 UseLibraryHeaders [ FDirName libfdt ] ;
 
+local libFDTSources =
+	fdt.c
+	fdt_ro.c
+	fdt_rw.c
+	fdt_strerror.c
+	fdt_sw.c
+	fdt_wip.c
+;
+
 KernelMergeObject kernel_platform_u-boot.o :
 	platform.cpp
+	fdt_support.cpp
 	openfirmware.cpp
+	$(libFDTSources)
 ;
+
+SEARCH on [ FGristFiles $(libFDTSources) ]
+	= [ FDirName $(HAIKU_TOP) src libs libfdt ] ;
+

src/system/kernel/platform/u-boot/fdt_support.cpp

@@ -15,6 +15,10 @@ extern "C" {
 #include <libfdt_env.h>
 };
 
+#ifndef _BOOT_MODE
+/* the bootloader has it in asm code to avoid it ending up in .bss */
+void *gFDT;
+#endif
 
 extern "C" void dump_fdt(const void *fdt);