samples: move architecture specific samples to arch/

smp and mpu are architecture specific samples and do not apply to
majority of support platforms, so move them to arch/.

Signed-off-by: Anas Nashif <anas.nashif@intel.com>

samples/arch/index.rst

@@ -0,0 +1,10 @@
+.. _arch-samples:
+
+Architecture Dependent Samples
+##############################
+
+.. toctree::
+   :maxdepth: 1
+   :glob:
+
+   **/*

samples/index.rst

@@ -17,14 +17,12 @@ Samples and Demos
    sensor/*
    arch/*
    boards/*
-   mpu/*
    drivers/drivers.rst
    application_development/*
    shields/*
    portability/*
    posix/*
    kernel/*
-   smp/*
    tfm_integration/tfm_integration.rst
 
 .. comment