configure.ac: bump required etnaviv libdrm version to 2.4.82

The following changes need the modifier definitions for the Vivante tiled
formats, which are shipped with libdrm 2.4.82.

Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
diff --git a/configure.ac b/configure.ac
index c5803e0..0443efd 100644
--- a/configure.ac
+++ b/configure.ac
@@ -79,7 +79,7 @@
 LIBDRM_NVVIEUX_REQUIRED=2.4.66
 LIBDRM_NOUVEAU_REQUIRED=2.4.66
 LIBDRM_FREEDRENO_REQUIRED=2.4.74
-LIBDRM_ETNAVIV_REQUIRED=2.4.80
+LIBDRM_ETNAVIV_REQUIRED=2.4.82
 
 dnl Versions for external dependencies
 DRI2PROTO_REQUIRED=2.8