Fix attach-twice.c testcase for AIX.

Currently, in AIX attach-twice.exp testcase is untested due to the below error.
gdb/testsuite/gdb.base/attach-twice.c:43:7: error: too few arguments to function 'ptrace'

This is because in AIX ptrace has five arguments. This patch is a fix for the same such that
this test case runs in AIX and other targets as well.
1 file changed