riscv: Remove ARCH_WANT_OPTIONAL_GPIOLIB select

riscv: Remove ARCH_WANT_OPTIONAL_GPIOLIB select

The ARCH_WANT_OPTIONAL_GPIOLIB symbol was removed in commit 162770661ae0
("gpio: delete ARCH_[WANTS_OPTIONAL|REQUIRE]_GPIOLIB"). GPIOLIB should
just be selected explicitly if needed.

Remove the ARCH_WANT_OPTIONAL_GPIOLIB select from RISCV.

See commit 03313ad93ffe ("x86: Do away with
ARCH_[WANT_OPTIONAL|REQUIRE]_GPIOLIB") and commit 9ed7622474 ("arm64: do
away with ARCH_[WANT_OPTIONAL|REQUIRE]_GPIOLIB") as well.

Discovered with the
https://github.com/ulfalizer/Kconfiglib/blob/master/examples/list_undefined.py
script.

Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Ulf Magnusson <ulfalizer@gmail.com>
Signed-off-by: Palmer Dabbelt <palmer@dabbelt.com>