tests: posix: fs: Decrease ramdisk size, increase stack size

This test seems to be fine in the current master, but doing
development, it easily starts to overflow RAM of some boards and/or
crash due to stack checks. So, decrease the ramdisk (the biggest
eater of RAM here) from default 96K to 80K, and bump main stack
size proactively.

Signed-off-by: Paul Sokolovsky <paul.sokolovsky@linaro.org>
1 file changed