Remove unnecessary and obsolete configure.ac directives

Also enable silent rules where missing

Change-Id: Ia521886815c862b013f01df4cc18fd8a298aaaa1
Signed-off-by: Damjan Marion <damarion@cisco.com>
diff --git a/vppapigen/configure.ac b/vppapigen/configure.ac
index 57065b8..16ad59d 100644
--- a/vppapigen/configure.ac
+++ b/vppapigen/configure.ac
@@ -5,10 +5,10 @@
 
 AC_INIT(vppapigen, 1.0)
 AM_INIT_AUTOMAKE
+AM_SILENT_RULES([yes])
 
 # Checks for programs.
 AC_PROG_CC
 AC_PROG_YACC
-AM_PROG_CC_C_O
 
 AC_OUTPUT([Makefile])