astlpc: Introduce protocol v3 with integrity checks

v3 of the binding adds a CRC-32 value as a medium-specific trailer to
each packet passing over the binding interface.

The patch includes a naive bit-shift implementation of CRC-32, we can
improve it later as necessary.

Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
Change-Id: I93a95bccef30010d56e10e29b6d84554268ab7af
diff --git a/Makefile.am b/Makefile.am
index d630078..fc8e937 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -12,7 +12,7 @@
 endif
 
 if LIBMCTP_BINDING_astlpc
-libmctp_la_SOURCES += astlpc.c
+libmctp_la_SOURCES += astlpc.c crc32.c
 include_HEADERS += libmctp-astlpc.h
 endif