FreeRTOS: properly read on big endian systems.

FreeRTOS: properly read on big endian systems.

Remember, don't cast your pointers between types of different sizes!

While the FreeRTOS handlers attempt to account for different pointer and
list widths, the types used are always fixed, so this will _remain_
broken if/when someone targets FreeRTOS on 8/16/64 bit targets. (Note
that this patch does not _change_ that, it was fixed to 32bit before as
well)

In the meantime, this properly handles 32bit reads on a mips BE system
(ath79) as well as remaining fully functional on x86_64.

Change-Id: I677bb7130e25dccb7c1bee8fabaee27371494d00
Signed-off-by: Karl Palsson <karlp@etactica.com>
Reviewed-on: http://openocd.zylin.com/5842
Reviewed-by: Antonio Borneo <borneo.antonio@gmail.com>
Tested-by: jenkins