[eribradl]

Add a board profile for the DSD TECH SH-C31A, an STM32G431 USB to CAN FD adapter derived from the CANable 2.0 design. Zephyr support for the board was added in zephyrproject-rtos/zephyr#121958.

• Channel 0 uses FDCAN1. The RXD and TXD LEDs show RX and TX activity.
• Hardware timestamps come from TIM2 with a prescaler of 159, i.e. 1 MHz from the 160 MHz APB1 clock, as on mks_canable_v20.
• The adapter is bus-powered.
• The firmware fits in the 64 KiB of flash without LTO, so unlike mks_canable_v20 this profile does not enable it.

Testing:

• Builds without warnings for dsdtech_shc31a on Zephyr main (f545c1ca45). Flash use is 56592 bytes by default and 56676 bytes with CONFIG_CAN_MANUAL_RECOVERY_MODE=y.
• Hardware: an SH-C31A ran this build with a DFU detach hook added for remote reflashing, on a Linux 6.12 gs_usb host, against a second adapter at CAN FD 1 Mbit/s nominal and 5 Mbit/s data with BRS. 1000 of 1000 64-byte frames went through in each direction, and every frame the adapter sent was echoed. Over 200 frames sent 5 ms apart, the hardware RX timestamps tracked the host clock to within 0.2%.