gpio: intel_gpio: Clear tx state bit when setting output

Add missing 'PAD_CFG0_TX_STATE' to the clear mask for pcr_clrsetbits32().
Otherwise this bit cannot be cleared again after it has been set once.

Signed-off-by: Wolfgang Wallner <wolfgang.wallner@br-automation.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>