CVE-2026-72273: fbdev: efifb: fix memory leak in efifb_probe()

In the Linux kernel, the following vulnerability has been resolved:

fbdev: efifb: fix memory leak in efifbprobe()

Since commit 73ce73c30ba9 ("fbdev: Transfer video= option strings to caller; clarify ownership") the string returned from fbgetoptions() is expected to be freed by the caller, but the string is not freed in efifbprobe(). Fix that by freeing the option string after setup.