Fix: Increase pwmsim stack again to avoid load_mon warning

[philipoe]

Issue:

PR #9007 decreased the stack size of the pwmsim module, however, the load_mon app now gives a "pwmsim low on stack warning" when running HIL using the current master branch (pwm sim has 1000->980 bytes stack, and needs ca 736 bytes, the load_mon required stack size margin is 300 bytes). I used px4fmu-v2 with rev. 3 silicon, but that should not matter.

Solutions:

1. Apply this PR -> Done
2. Decrease the required stack size margin in load_mon

@dagar @LorenzMeier Your decision.

[LorenzMeier]

We need 300 Bytes margin, so this is good.