try to open fd in gpio_get_fd
try to open fd in gpio_get_fd

users expect to retrive a valid fd if get_gpio_fd is called.

But the fd might be uninitialized, because only gpio_open was called.
gpio_open just exports the gpio, but doesn't open the fd. The fd will
be opened on first access.

Signed-off-by: Manuel Traut <5b9fefc5e24c8c0032a4b1b435e37d15daf2b05f@linutronix.de>

Linutronix/libgpio,Linutronix/libgpio