Move crypto toolbox functions into separate file

am: 9bc641359a

Change-Id: If008cd16c1ea637ae43b3a9c3548a503b636b7a2

diff --cc stack/Android.bp
index 75e6555,28c1b72..f27ae05
--- 1/stack/Android.bp
--- 2/stack/Android.bp
+++ b/stack/Android.bp
@@@ -293,10 -294,8 +294,11 @@@ cc_test 
      ],
      srcs: [
          "smp/smp_keys.cc",
+         "smp/crypto_toolbox.cc",
          "smp/aes.cc",
 +        "smp/p_256_curvepara.cc",
 +        "smp/p_256_ecc_pp.cc",
 +        "smp/p_256_multprecision.cc",
          "smp/smp_api.cc",
          "smp/smp_cmac.cc",
          "smp/smp_main.cc",