KVM: selftests: Rename pta (short for perf_test_args) to args

Rename the local variables "pta" (which is short for perf_test_args) for
args. "pta" is not an obvious acronym and using "args" mirrors
"vcpu_args".

Suggested-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: David Matlack <dmatlack@google.com>
Reviewed-by: Sean Christopherson <seanjc@google.com>
Link: https://lore.kernel.org/r/20221012165729.3505266-3-dmatlack@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>