configure: Fix hard-coded enabled v4l2 probe on Linux/ARM

configure: Fix hard-coded enabled v4l2 probe on Linux/ARM

Currently, enable_v4l2_probe is hard-coded to "yes" on linux, platforms
arm and aarch64. This even overrides the --disable-v4l2-probe argument.
As a result, it is impossible to disable v4l2_probe. It becomes a problem
for use-cases, when startup time is critical, because the v4l2_probe
feature increases the initialization time.

This commit makes the v4l2_probe feature configurable.
On linux, platforms arm and aarch64, the default value is still "yes".
But now it can be disabled by the --disable-v4l2-probe argument.

https://bugzilla.gnome.org/show_bug.cgi?id=795200