pinctrl: mlxbf3: remove broken Kconfig 'select'

The new pinctrl driver selects GPIO_MLXBF3, but that can not be enabled yet because
the MELLANOX_PLATFORM symbol does not exist in the tree:

WARNING: unmet direct dependencies detected for GPIO_MLXBF3
  Depends on [n]: GPIOLIB [=y] && PCI [=n] && (MELLANOX_PLATFORM [=n] && ARM64 [=y] || COMPILE_TEST [=y])
  Selected by [y]:
  - PINCTRL_MLXBF3 [=y] && PINCTRL [=y] && (MELLANOX_PLATFORM [=n] && ARM64 [=y] || COMPILE_TEST [=y])

As it turns out, the pinctlr driver still builds fine without this, so just
remove the select statement.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Link: https://lore.kernel.org/r/20230619082104.699331-1-arnd@kernel.org


Signed-off-by: Linus Walleij <linus.walleij@linaro.org>