x86: efi: Tweak the code used for the 64-bit EFI app

Add an empty CPU init function to avoid fiddling with low-level CPU
features in the app. Set up the C runtime correctly for 64-bit use
and avoid clearing BSS, since this is done by EFI when U-Boot is loaded.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/arch/x86/lib/relocate.c b/arch/x86/lib/relocate.c
index 6fe5151..9060d19 100644
--- a/arch/x86/lib/relocate.c
+++ b/arch/x86/lib/relocate.c
@@ -35,6 +35,7 @@
 	return 0;
 }
 
+#ifndef CONFIG_EFI_APP
 int clear_bss(void)
 {
 	ulong dst_addr = (ulong)&__bss_start + gd->reloc_off;
@@ -46,6 +47,7 @@
 
 	return 0;
 }
+#endif
 
 #if CONFIG_IS_ENABLED(X86_64)
 static void do_elf_reloc_fixups64(unsigned int text_base, uintptr_t size,