gpiolib: move validation of line handle flags into helper function

Move validation of line handle flags into helper function.
This reduces the size and complexity of linehandle_create and allows the
validation to be reused elsewhere.

Signed-off-by: Kent Gibson <warthog618@gmail.com>
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
1 file changed