Merge #188

188: boards: opentitan: Update the SRAM layout r=alistair23 a=alistair23

As Tock for OT has gotten larger the SRAM allocated for apps has moved
up in memory. Let's update the linker script to better match what Tock
is allocating.

Signed-off-by: Alistair Francis <alistair.francis@wdc.com>

Co-authored-by: Alistair Francis <alistair.francis@wdc.com>