NPTL: ARC support

Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
Adjust for TP Reg not pointing to TCB

Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
ARC/nptl: Enable TLS tests

Signed-off-by: Vineet Gupta <vgupta@synopsys.com>