tests: Rewrite .gitignore file

The file was already outdated again, so rewrite it to ignore
anything but c, h and sh files that start with "test-".

Signed-off-by: Johannes Berg <johannes.berg@intel.com>

tests/.gitignore

@@ -1,16 +1,3 @@
-test-aes
-test-asn1
-test-base64
-test-https
-test-https_server
-test-list
-test-md4
-test-md5
-test-milenage
-test-ms_funcs
-test-printf
-test-rc4
-test-sha1
-test-sha256
-test-x509
-test-x509v3
+test-*
+!test-*.[ch]
+!test-*.sh