CVE-2025-68339 atm/fore200e: Fix possible data race in fore200e_open()

In the Linux kernel, the following vulnerability has been resolved: atm/fore200e: Fix possible data race in fore200eopen Protect access to fore200e-availablecellrate with ratemtx lock in the error handling path of fore200eopen to prevent a data race. The field fore200e-availablecellrate is a shar...