U-Boot: move gUImage and gFDT back to BSS section

No need for this trick anymore.

src/system/boot/platform/u-boot/arch/arm/shell.S

@@ -75,16 +75,10 @@ SYMBOL_END(_start_common)
 SYMBOL(gUBootGlobalData):
 	.long   0
 SYMBOL_END(gUBootGlobalData)
-SYMBOL(gUImage):
-	.long   0
-SYMBOL_END(gUImage)
 SYMBOL(gUBootOS):
 //XXX: bug? Using .byte makes the next asm symbol
 // to be at the same address
 //	.byte	0
 	.long   0
 SYMBOL_END(gUBootOS)
-SYMBOL(gFDT):
-	.long   0
-SYMBOL_END(gFDT)
 

src/system/boot/platform/u-boot/arch/ppc/shell.S

@@ -50,16 +50,10 @@ SYMBOL_END(_start_common)
 SYMBOL(gUBootGlobalData):
 	.long   0
 SYMBOL_END(gUBootGlobalData)
-SYMBOL(gUImage):
-	.long   0
-SYMBOL_END(gUImage)
 SYMBOL(gUBootOS):
 //XXX: bug? Using .byte makes the next asm symbol
 // to be at the same address
 //	.byte	0
 	.long   0
 SYMBOL_END(gUBootOS)
-SYMBOL(gFDT):
-	.long   0
-SYMBOL_END(gFDT)
 

src/system/boot/platform/u-boot/start.cpp

@@ -63,10 +63,11 @@ extern "C" void dump_fdt(const void *fdt);
 
 // declared in shell.S
 // those are initialized to NULL but not in the BSS
-extern struct image_header *gUImage;
 extern uboot_gd *gUBootGlobalData;
 extern uint32 gUBootOS;
-extern void *gFDT;
+
+struct image_header *gUImage;
+void *gFDT;
 
 static uint32 sBootOptions;