pinctrl: k210: Fix bias-pull-up

Using bias-pull-up would actually cause the pin to have its pull-down
enabled. Fix this.

Original Linux patch by Sean Anderson:
https://lore.kernel.org/linux-gpio/20220209182822.640905-1-seanga2@gmail.com/



Fixes: 7224d5cc ("pinctrl: Add support for Kendryte K210 FPIOA")
Signed-off-by: Niklas Cassel <niklas.cassel@wdc.com>
Reviewed-by: Sean Anderson <seanga2@gmail.com>