flash/nor: add lpc4300 variant to lpc2000 driver

This patch adds flash programming support for internal flash of the
LPC43x2/3/5/7 part, tested on a LPC4337 (also tested on a LPC1768
and LPC2468). It should also work with LPC1800's with onchip flash.
The "base" parameter of the "flash bank" command is now significant
for the lpc4300 variant and required to determine the bank number
parameter needed by the IAP routines.

NOTE: I could only program flash successfully when the chip is powered
with "P2_7" pulled low to put it in ISP mode.  When running from flash
(and not the ISP ROM), the target fails to halt and the sector erase
fails. This is similar to the behavior I remember when trying out the
spifi driver on a LPC4350... lots of power cycles to make progress, one
To burn, one to run.  So I am not confident my config is set up correctly.

Change-Id: I8a75ef1b95cedd5b5898b2dedff477f502fd19f3
Signed-off-by: Matt Dittrich <mdittrich.dev@gmail.com>
Reviewed-on: http://openocd.zylin.com/1126
Reviewed-by: Freddie Chopin <freddie.chopin@gmail.com>
Tested-by: jenkins