x86/split_lock: Don't warn about unknown split_lock_detect parameter

x86/split_lock: Don't warn about unknown split_lock_detect parameter

The split_lock_detect command line parameter is handled in sld_setup() shortly
after cpu_parse_early_param() but still before parse_early_param().

Add a dummy parsing function so that parse_early_param() doesn't later
complain about the "unknown" parameter split_lock_detect=, and pass it along
to init.

  [ bp: Massage commit message. ]

Signed-off-by: Ronan Pigott <ronan@rjp.ie>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://patch.msgid.link/20260405181807.3906-1-ronan@rjp.ie