efi_loader: don't use memmove() in efi_var_mem_del()

efi_var_mem_del() is in __efi_runtime because it would be needed for a
runtime implementation of SetVariable(). memmove() is not in __efi_runtime.
So we should not use it in efi_var_mem_del().

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
diff --git a/lib/efi_loader/efi_runtime.c b/lib/efi_loader/efi_runtime.c
index 91a4551..78fd801 100644
--- a/lib/efi_loader/efi_runtime.c
+++ b/lib/efi_loader/efi_runtime.c
@@ -144,6 +144,8 @@
  *
  * At runtime memcpy() is not available.
  *
+ * Overlapping memory areas can be copied safely if src >= dest.
+ *
  * @dest:	destination buffer
  * @src:	source buffer
  * @n:		number of bytes to copy
diff --git a/lib/efi_loader/efi_var_mem.c b/lib/efi_loader/efi_var_mem.c
index 856e5e1..bfa8a56 100644
--- a/lib/efi_loader/efi_var_mem.c
+++ b/lib/efi_loader/efi_var_mem.c
@@ -120,7 +120,8 @@
 	       ALIGN((uintptr_t)data + var->length, 8);
 	efi_var_buf->length -= (uintptr_t)next - (uintptr_t)var;
 
-	memmove(var, next, (uintptr_t)last - (uintptr_t)next);
+	/* efi_memcpy_runtime() can be used because next >= var. */
+	efi_memcpy_runtime(var, next, (uintptr_t)last - (uintptr_t)next);
 	efi_var_buf->crc32 = crc32(0, (u8 *)efi_var_buf->var,
 				   efi_var_buf->length -
 				   sizeof(struct efi_var_file));