Drop SD_ aliases for SDIO signals (SD_CMD, SD_DAT0..3) on RP2040 Adalogger board

[mikeysklar]

Per discussion in #11090, the Adalogger boards carry SD_-prefixed aliases for SDIO-only signals, and we should drop them at the next major release so SD_ consistently means SPI and SDIO_ means SDIO.

Naming rule

Bus	Convention	Names
SPI	abbreviated, SPI terms	SD_CLK, SD_MOSI, SD_MISO, SD_CS
SDIO	spelled-out, SDIO terms	SDIO_CLOCK, SDIO_COMMAND, SDIO_DATA0..3

The names to remove are the hybrids — the SPI SD_ prefix on SDIO-only concepts, which have no SPI meaning:

• SD_CMD
• SD_DAT0, SD_DAT1, SD_DAT2, SD_DAT3

SD_CLK stays (CLK is a real SPI term; there is no SD_CLOCK anywhere in the tree). Affected boards: adafruit_feather_rp2040_adalogger, adafruit_feather_rp2350_adalogger. The SDIO_* names already exist on Metro RP2040/RP2350 and Fruit Jam.

Learning Guide usage check (Adafruit_Learning_System_Guides)

Name	CircuitPython guide references	Safe to drop?
SD_DAT0..3	0	✅ yes
SD_CMD	0	✅ yes
SD_CLK	2	⚠️ keep (SPI clock)

The two SD_CLK uses are Feather_RP2040_Adalogger/CircuitPython_SD_Card_{Read,Write}/code.py, both busio.SPI(board.SD_CLK, board.SD_MOSI, board.SD_MISO) — SPI, unaffected. The PIN_SD_DAT3_CS hits under Factory_Tests/ and runcpm-* are Arduino macros (pins_arduino.h), a separate namespace, so not affected.

cc @dhalbert @FoamyGuy

[tannewt]

Let's get these added to this guide: https://learn.adafruit.com/how-to-add-a-new-board-to-circuitpython/pin-and-device-names and update the learn guides once the consistent naming is in a stable release.

Removing the old aliases isn't critical but it'd be good to get standardized.

[mikeysklar]

pin-and-device-names guide page updated with preferred names for SPI and SDIO.

[tannewt]

pin-and-device-names guide page updated with preferred names for SPI and SDIO.

Thank you!