With all the variation in chips and boards it's tedious to copy and
redefine linker scripts for every option. Making linker scripts more
modular also opens up more possibilities, like enabling/disabling the
flash file system from the Makefile - or even defining it's size from a
Makefile argument (FS_SIZE=12 for a 12kB filesystem if tight on space).
The nrf51x22_256k_16k_s110_8.0.0.ld had a stack size of only 1kB, which
is way too low. Additionally, the indicated _minimum_stack_size (set at
2kB for that chip) isn't respected.
This commit sets the heap end based on the stack size (heap end = RAM
end - stack size) making it much easier to configure.
Additionally, the stack/heap size of nrf52 chips has been set to a more
sane value of 8kB.
Ayke van Laethem