Cortex-R: Force usage of physical memory read/write since there is no MMU

Cortex-R: Force usage of physical memory read/write since there is no MMU

Change-Id: I69d6e6301ab66744258fe650a76c7241bebe00a8
Signed-off-by: Evan Hunter <ehunter@broadcom.com>
Reviewed-on: http://openocd.zylin.com/3203
Tested-by: jenkins
Reviewed-by: Girts Folkmanis <opensource@girts.me>
Reviewed-by: Matthias Welwarsky <matthias@welwarsky.de>
Reviewed-by: Jiri Kastner <cz172638@gmail.com>
Reviewed-by: Paul Fertser <fercerpav@gmail.com>