Updat and move pins_SOVOL_V131.h

[ellensp]

Description

The SOVOL V131 motherboard is basically a clone of the Creality V4 with the addition of TMC UART pins (and a GD32)

Move file to pins/gd32f1

Include Creality_V4 pins and simplify pins_SOVOL_V131

Requirements

BOARD_SOVOL_V131

Benefits

Arguably neater.

Related Issues

#25267

[thinkyhead]

As this GD32F1 processor is intended to be a mostly-compatible clone of STM32F1, and we are still building with the ST-Micro reference platform, I'm not sure we need to move GD32F1 into a separate folder, as if it represented a different MCU family. But, what other distinctions are there for GD32 that could make them worthy of their own separate category?

[thinkyhead]

Hmm, I see we're already doing that for BOARD_TRIGORILLA_V006. I guess we'll carry on, then!

[ellensp]

This new e_error doesn't seem to make sense

  #error "SOVOL V131 only supports 1 hotend / E-stepper."
  #define E_ERROR 1

Is E_ERROR ever set? it is after an #error which stops pre-processing

[thinkyhead]

This new e_error doesn't seem to make sense

It's set in order to suppress a second #error message that would potentially be confusing…

#if !E_ERROR && (HAS_MULTI_HOTEND || E_STEPPERS > 1)
  #error "Creality v4 only supports 1 hotend / E stepper."
#endif

Preprocessing isn't actually stopped by #error. It's stopped by a certain number of #error as set by -fmax-errors=5.

This can be demonstrated with:

#define BLAH

#if ENABLED(BLAH)
  #error "ERROR TEST 1"
  #define DID_ERROR 1
#endif

#if !DID_ERROR && ENABLED(BLAH)
  #error "ERROR TEST 2"
#endif