objtool: Fix obsolete reference to CONFIG_X86_SMAP

CONFIG_X86_SMAP no longer exists.  For objtool's purposes it has been
replaced with CONFIG_HAVE_UACCESS_VALIDATION.

Fixes: 03f16cd020 ("objtool: Add CONFIG_OBJTOOL")
Reported-by: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Link: https://lore.kernel.org/r/44c57668768c1ba1b4ba1ff541ec54781636e07c.1654101721.git.jpoimboe@kernel.org

lib/Kconfig.ubsan

@@ -94,7 +94,7 @@ config UBSAN_UNREACHABLE
 	bool "Perform checking for unreachable code"
 	# objtool already handles unreachable checking and gets angry about
 	# seeing UBSan instrumentation located in unreachable places.
-	depends on !(OBJTOOL && (STACK_VALIDATION || UNWINDER_ORC || X86_SMAP))
+	depends on !(OBJTOOL && (STACK_VALIDATION || UNWINDER_ORC || HAVE_UACCESS_VALIDATION))
 	depends on $(cc-option,-fsanitize=unreachable)
 	help
 	  This option enables -fsanitize=unreachable which checks for control