util/iteflash: ftdi_usb_purge_buffers is deprecated
util/iteflash: ftdi_usb_purge_buffers is deprecated

According to
http://developer.intra2net.com/mailarchive/html/libftdi/2018/msg00105.html
there has been a renaming going on. To support both old and new libftdi
disable the deprecation warning (that we then promote to an error).

Signed-off-by: Patrick Georgi <bc411205f21846a74924ee7b489c75617ec76078@google.com>
Change-Id: I1df660cb7e8d8c8a410a8d9ee5e4a45108dad493
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/2692690
Tested-by: Patrick Georgi <bc411205f21846a74924ee7b489c75617ec76078@chromium.org>
Reviewed-by: Paul Fagerburg <d8c44b60afb21c60f56d931aa690ca1cf34910c8@chromium.org>
Reviewed-by: Patrick Georgi <bc411205f21846a74924ee7b489c75617ec76078@chromium.org>
Commit-Queue: Patrick Georgi <bc411205f21846a74924ee7b489c75617ec76078@chromium.org>

coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec