userspace: remove APP_SHARED_MEM Kconfig

This is an integral part of userspace and cannot be used
on its own. Fold into the main userspace configuration.

Signed-off-by: Andrew Boie <andrew.p.boie@intel.com>
diff --git a/kernel/compiler_stack_protect.c b/kernel/compiler_stack_protect.c
index 5f20ad2..c2869b5 100644
--- a/kernel/compiler_stack_protect.c
+++ b/kernel/compiler_stack_protect.c
@@ -46,7 +46,7 @@
  * Symbol referenced by GCC compiler generated code for canary value.
  * The canary value gets initialized in _Cstart().
  */
-#ifdef CONFIG_APP_SHARED_MEM
+#ifdef CONFIG_USERSPACE
 K_APP_DMEM(z_libc_partition) uintptr_t __stack_chk_guard;
 #else
 __noinit uintptr_t __stack_chk_guard;