bootstd: Use bootdev instead of bootdevice

It seems better to call this a 'bootdev' since this is name used in the
documentation. The older 'Bootdevice' name is no-longer used and may cause
confusion with the 'bootdevice' environment variable.

Update throughout to use bootdev.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>

net/eth_bootdev.c

@@ -1,6 +1,6 @@
 // SPDX-License-Identifier: GPL-2.0+
 /*
- * Bootdevice for ethernet (uses PXE)
+ * Bootdev for ethernet (uses PXE)
  *
  * Copyright 2021 Google LLC
  * Written by Simon Glass <sjg@chromium.org>