configure.ac: remove redundant declaration "HAVE_ISO9660"

Makefile.am

@@ -753,7 +753,7 @@ libarchive_a_SOURCES += \
 	src/archive/plugins/ZzipArchivePlugin.hxx
 endif
 
-if HAVE_ISO9660
+if ENABLE_ISO9660
 libarchive_a_SOURCES += \
 	src/archive/plugins/Iso9660ArchivePlugin.cxx \
 	src/archive/plugins/Iso9660ArchivePlugin.hxx

configure.ac

@@ -785,10 +785,7 @@ dnl --------------------------------- iso9660 ---------------------------------
 MPD_ENABLE_AUTO_PKG(iso9660, ISO9660, [libiso9660],
 	[libiso9660 archive plugin], [libiso9660 not found])
 
-AM_CONDITIONAL(HAVE_ISO9660, test x$enable_iso9660 = xyes)
 if test x$enable_iso9660 = xyes; then
-	AC_DEFINE(HAVE_ISO9660, 1, [Define to have ISO9660 archive support])
-
 	AC_PATH_PROG(MKISOFS, mkisofs, no)
 else
 	MKISOFS="no"

src/archive/ArchiveList.cxx

@@ -35,7 +35,7 @@ const ArchivePlugin *const archive_plugins[] = {
 #ifdef ENABLE_ZZIP
 	&zzip_archive_plugin,
 #endif
-#ifdef HAVE_ISO9660
+#ifdef ENABLE_ISO9660
 	&iso9660_archive_plugin,
 #endif
 	nullptr