x86: Use loops instead of memcpy/memset in board_init_f

Provides a small speed increase and prepares for fully relocatable image.
Downside is the TEXT_BASE, bss, load address etc must ALL be aligned on a
a 4-byte boundary which is not such a terrible restriction as everything
is already 4-byte aligned anyway

board/eNET/u-boot.lds

@@ -58,7 +58,8 @@ SECTIONS
 	. = ALIGN(4);
 	__bss_start = ABSOLUTE(.);
 	.bss (NOLOAD) : { *(.bss) }
-	__bss_size = SIZEOF(.bss);
+	. = ALIGN(4);
+	__bss_end = ABSOLUTE(.);
 
 	. = ALIGN(4);
 	__rel_dyn_start = .;