build: Always allow switching log level at runtime

There are no parts of libfprint that are so resource intensive that we'd
want to disable logging. This avoids (hopefully rare) cases where
compiled versions of libfprint are distributed with logging completely
disabled, and thus can't be debugged.

meson_options.txt

@@ -14,10 +14,6 @@ option('x11-examples',
        description: 'Whether to build X11 example applications',
        type: 'boolean',
        value: true)
-option('log',
-       description: 'Message logging',
-       type: 'boolean',
-       value: true)
 option('debug_log',
        description: 'Debug message logging',
        type: 'boolean',