Remove bogus duplicate CONFIG_LGUEST_GUEST entry.

It was moved to arch/x86/lguest/Kconfig, but I lost the deletion part in a
patch suffle.  My confused one-liner "fix" to turn it on is also reverted:
84f7466e

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>