gpio: sim: fix memory corruption when adding named lines and unnamed hogs

When constructing the sim, gpio-sim constructs an array of named lines,
sized based on the largest offset of any named line, and then initializes
that array with the names of all lines, including unnamed hogs with higher
offsets.  In doing so it writes NULLs beyond the extent of the array.

Add a check that only named lines are used to initialize the array.

Fixes: cb8c474e

 ("gpio: sim: new testing module")
Signed-off-by: Kent <Gibson&lt;warthog618@gmail.com>
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>