puf_sram only relies on an uninitialized chunk of memory.
This means to enable it we just have to hook up puf_sram_init().
All memory after __bss_end should be uninitialized at startup, so
just use that.
At the time of configuration, the pthread-reaper uses '164' bytes of
stack when 'idle' stack is only '160'. By having double it gives some
margin.
ps
pid | name | state Q | pri | stack ( used) | base addr | current
1 | idle | pending Q | 15 | 160 ( 128) | 0x4000007c | 0x4000009c
2 | main | running Q | 7 | 2560 ( 1232) | 0x4000011c | 0x4000095c
3 | pthread-reaper | bl rx _ | 0 | 320 ( 164) | 0x40000bac | 0x40000c48
| SUM | | | 3040 ( 1524)
- removed ISR_STACKSIZE define where unused (set to 0)
- removed thread_arch_isr_stack_usage(), thread_arch_isr_stack_start(),
and/or thread_arch_isr_stack_pointer() where not implemented
