fixed enable/disable for input pins

Now you can disable a single bank of input pins
Fixed I2C bug where .granted() was problematic

The state machine was getting triggered when I didn't expect it, causing
upper layers to get signaled spuriously. I still think there is a bug in
the msp i2c code or in nesc, because i don't know why .granted() was
getting called when the i2c_state == I2C_ST_SET_PIN2.