Set output pin initial value based on pin's pinmux pullup/pulldown setup

Some of FDT blobs for AM335x-based devices use pinmux pullup/pulldown
flag to setup initial GPIO ouputp value, e.g. 4DCAPE-43 sets LCD DATAEN
signal this way. It works for Linux because Linux driver does not enforce
pin direction until after it's requested by consumer. So input with pullup
flag set acts as output with GPIO_HIGH value

Reviewed by: loos