lpc2000: Fix flash programming fail on LPC4300 internal flash

lpc2000: Fix flash programming fail on LPC4300 internal flash

LPC43xx with internal flash parts model needs "IAP Init(49)"Command
before erase & write internal flash.Tested on a LPC4337 and LPC4357.

Change-Id: I48620ce12e578c61a3ca1adcd48815c1f71c35bb
Signed-off-by: Nemui Trinomius <nemuisan_kawausogasuki@live.jp>
Reviewed-on: http://openocd.zylin.com/1784
Tested-by: jenkins
Reviewed-by: Jens Bauer <jens@gpio.dk>
Reviewed-by: Mathias Küster <kesmtp@freenet.de>
Reviewed-by: Spencer Oliver <spen@spen-soft.co.uk>