Disable ramdump with debug policy

This CL disables ramdump if debug policy doesn't explicitly
enables ramdump via ramdump prop in the /avf/guest/common node.

The virtualization service always provides crashkernel=17M via
kernel command, so this CL removes crashkernel=17MB in the
microdroid's bootargs in the /chosen node.

Here's the test result on my machine with MicrodroidTestApp.

  - Before the CL (or this CL + ramdump is enabled)
    $ adb shell /proc/meminfo
    MemTotal:         212968 kB
    MemFree:          138336 kB
    MemAvailable:     171980 kB

  - With this CL + ramdump is disabled
    $ adb shell /proc/meminfo
    MemTotal:         230372 kB
    MemFree:          165240 kB
    MemAvailable:     192648 kB

Bug: 243630590
Test:  Boot microdroid with following AVF debug policies \
  - AVF debug policy exists, and ramdump=<1> \
  - AVF debug policy exists, and ramdump=<0> \
  - No AVF debug policy
Change-Id: Ia486448b5513c2d5662a4f16ddb3334b20913329
diff --git a/pvmfw/src/main.rs b/pvmfw/src/main.rs
index 24c36b3..faadd37 100644
--- a/pvmfw/src/main.rs
+++ b/pvmfw/src/main.rs
@@ -22,6 +22,7 @@
 
 mod avb;
 mod config;
+mod debug_policy;
 mod dice;
 mod entry;
 mod exceptions;