pinctrl: renesas: Add generic support for resizable buses

The VIN_DATA_PIN_GROUP() macro and vin_data{12,16,} unions are used to
define multiple VIN data groups with different numbers of lanes, while
referring to a single array of data pins, thus saving memory.

However, the same feature would be useful for other resizable buses,
like MMC, SDHI, QSPI, LCD, BSC, ...

Rework the mechanism for generic use:
  - Use the new SH_PFC_PIN_GROUP_SUBSET() helper to remove the need for
    bus-specific unions,
  - Rename VIN_DATA_PIN_GROUP() to BUS_DATA_PIN_GROUP(),
  - Rename the macro parameters to better reflect their purposes,
  - Move the macro up, where it belongs.

Update all individual pin control drivers for the above changes.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/cccfcfd01eb8ab7a587b084c4ddbf97293bd7291.1640269757.git.geert+renesas@glider.be