tar: clean up run-ptest

I'm not sure why the script was running ./atconfig ./atlocal ./testsuite,
as atconfig just sets some variables and ignores the arguments.

(From OE-Core rev: 0e2c41724197de3de89d762cb1b648c09839af53)

Signed-off-by: Ross Burton <ross.burton@arm.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/recipes-extended/tar/tar/run-ptest

@@ -1,14 +1,8 @@
 #!/bin/sh
 
-# Define tar test work dir
-WORKDIR=@PTEST_PATH@/tests/
+cd @PTEST_PATH@/tests/
 
-# Run test
-cd ${WORKDIR}
-./atconfig ./atlocal ./testsuite
-
-# clear log
-rm -rf testsuite.dir
-rm -rf testsuite.log
+# Clear old data
+rm -rf testsuite.dir testsuite.log
 
 ./testsuite --am-fmt