configure: remove postproc-generic

This option is vestigial and is unreferenced.

Change-Id: I8bd27cb674c263e9a86fb43244003a9b9df3ca9c

configure

diff --git a/configure b/configure
index f68f018..f74714d 100755
--- a/configure
+++ b/configure
@@ -231,7 +231,6 @@
     new_tokens
     runtime_cpu_detect
     postproc
-    postproc_generic
     multithread
     psnr
     ${CODECS}
@@ -270,7 +269,6 @@
     dc_recon
     new_tokens
     postproc
-    postproc_generic
     multithread
     psnr
     ${CODECS}