Do not use sparcv9 optimization flags for sparcv8 builds

Signed-off-by: Waldemar Brodkorb <wbx@openadk.org>

diff -Nur libmpeg2-0.5.1.orig/configure.ac libmpeg2-0.5.1/configure.ac
--- libmpeg2-0.5.1.orig/configure.ac	2008-07-18 16:30:17.000000000 +0200
+++ libmpeg2-0.5.1/configure.ac	2017-04-26 21:09:15.780838339 +0200
@@ -95,7 +95,7 @@
 		break
 	    fi
 	done;;
-    sparc-* | sparc64-*)
+    sparc64-*)
 	AC_DEFINE([ARCH_SPARC],,[sparc architecture])
 	TRY_CFLAGS="$OPT_CFLAGS -mcpu=ultrasparc -mvis"
 	AC_TRY_CFLAGS([$TRY_CFLAGS $CFLAGS],[OPT_CFLAGS="$TRY_CFLAGS"]);;