bmc: move Verification declaration out of single header

Split the interface declaration from the implementation declaration to
make it more obvious what would change to support more implementations.

Signed-off-by: Patrick Venture <venture@google.com>
Change-Id: I6452ad85513dad1431ef946b62936c1cea89c263
diff --git a/Makefile.am b/Makefile.am
index ca14c0a..cc7f110 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -43,7 +43,7 @@
 	firmware_handler.cpp \
 	file_handler.cpp \
 	internal/sys.cpp \
-	verify.cpp
+	verify_systemd.cpp
 
 if ENABLE_LPC_BRIDGE
 libfirmwareblob_common_la_SOURCES += lpc_handler.cpp