bugfix: build: s/enanble/enable/

Bugfix the typographical mistake the configure_ac.

Signed-off-by: Patrick Venture <venture@google.com>
Change-Id: I1f9fdb1c7674819e4e6676254f6a1c4735e8554c
diff --git a/configure.ac b/configure.ac
index 51cc165..e59fbec 100644
--- a/configure.ac
+++ b/configure.ac
@@ -73,7 +73,7 @@
 AC_ARG_ENABLE([tarball-ubi],
     AS_HELP_STRING([--enable-tarball-ubi],
                    [Enable tarball firmware update via Blobs]))
-AS_IF([test "x$enanble_tarball_ubi" = "xyes"], [
+AS_IF([test "x$enable_tarball_ubi" = "xyes"], [
     AX_APPEND_COMPILE_FLAGS([-DENABLE_TARBALL_UBI], [CXXFLAGS])
 ])