Documentation: asus-laptop.txt references an obsolete Kconfig item

The CONFIG_X86_UP_APIC option no longer exists.  Delete the
reference of it.

Cc: trivial@kernel.org
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

Documentation/laptops/asus-laptop.txt

@@ -151,8 +151,7 @@ Display switching
 
   Debugging:
   1) Check whether the Fn+F8 key:
-     a) does not lock the laptop (try disabling CONFIG_X86_UP_APIC or boot with
-        noapic / nolapic if it does)
+     a) does not lock the laptop (try a boot with noapic / nolapic if it does)
      b) generates events (0x6n, where n is the value corresponding to the
         configuration above)
      c) actually works