xfree86: device parser fix crash with duplicate "Clocks" property

[GermanAizek]

Related to issue: https://github.com/X11Libre/xserver/issues/1407

This commit fixes when processing the first line, the clock frequency value ptr->dev_clocks is 0. If the first line of the clock frequency contains 100 values, the clock frequency value ptr->dev_clocks will be 100. When processing the second row "Clocks", which contains, for example, 100 more values, the loop will start with i = 100. This will cause 72 values to be written outside the 128-element dev_block array, which will lead to buffer overflow and an emergency crash xserver.

[metux]

does this also need to be backported to maint-25.0 ?