x86/bugs: Remove dead code which might prevent from building

Clang, in particular, is not happy about dead code:

arch/x86/kernel/cpu/bugs.c:1830:20: error: unused function 'match_option' [-Werror,-Wunused-function]
 1830 | static inline bool match_option(const char *arg, int arglen, const char *opt)
      |                    ^~~~~~~~~~~~
1 error generated.

Remove a leftover from the previous cleanup.

Fixes: 02ac6cc8 ("x86/bugs: Simplify SSB cmdline parsing")
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Link: https://patch.msgid.link/20251024125959.1526277-1-andriy.shevchenko%40linux.intel.com