atl1c: refine start/enable code for MAC module

merge TXQ/RXQ/MAC start/enable code to one function as they
are started/enabled at the same time, just like stop/disable them
in the function of atl1c_stop_mac.

Signed-off-by: xiong <xiong@qca.qualcomm.com>
Tested-by: Liu David <dwliu@qca.qualcomm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>