lpc2000: Removed cmd51_can_xxxxb variables.

lpc2000: Removed cmd51_can_xxxxb variables.

Current flash driver can fail to write across the sector boundary.
This patch fixes "thisrun_bytes" set to "cmd51_dst_boundary" value instead of "cmd51_can_xxxxb"

Referred to SevenW's post and fix,thanks.
http://sourceforge.net/p/openocd/mailman/openocd-devel/thread/fa32e7d6654df22470dc5f4a3dbc984a%40familiebenschop.nl/#msg33594152

Tested on below listed chips.
LPC810,LPC811,LPC812,LPC824,LPC1115,LPC1343,LPC1347,LPC1227,
LPC1769,LPC1788,LPC54102,LPC4088 and LPC2388.

Change-Id: If1c6a1daa58ca27c405bd959a784e599a7a8f4d4
Signed-off-by: Nemui Trinomius <nemuisan_kawausogasuki@live.jp>
Reviewed-on: http://openocd.zylin.com/2607
Tested-by: jenkins
Reviewed-by: Jens Bauer <jens@gpio.dk>
Reviewed-by: Paul Fertser <fercerpav@gmail.com>