samples: basic/minimal: disable memory pool when MT=n

This adds the option to disable kernel memory pool when
multithreading is also not enabled. This saves some
code space.

Signed-off-by: Daniel Leung <daniel.leung@intel.com>
diff --git a/samples/basic/minimal/no-mt.conf b/samples/basic/minimal/no-mt.conf
index 312b390..0d20be6 100644
--- a/samples/basic/minimal/no-mt.conf
+++ b/samples/basic/minimal/no-mt.conf
@@ -1,3 +1,4 @@
 # Single-threaded, no timer support in the kernel
 
 CONFIG_MULTITHREADING=n
+CONFIG_KERNEL_MEM_POOL=n