Using stepper spindle with encoder

[dresco]

Appreciate the stepper spindle code is still flagged as experimental, just creating an issue so it's not overlooked..

I've found in the H7 driver, the combination of stepper spindle and encoder causes a hardfault when the spindle is started (I don't think context is populated?);

https:/dresco/STM32H7xx/blob/874cf6dbfe80b32b41d104f7257223c46c68ba86/Src/driver.c#L1383

Haven't had a chance to test with another driver, but the F4 code looks similar, so don't think it's a driver specific issue.