power(MemBlock): power optimization in MemBlock

[jin120811]

power optimization：
（1）use “withClockGate” instead of ClockGate in DCache
（2）reduce LSQ entries

[XiangShanRobot]

[Generated by IPC robot]
commit: 78e1f1d

commit	astar	copy_and_run	coremark	gcc	gromacs	lbm	linux	mcf	microbench	milc	namd	povray	wrf	xalancbmk
78e1f1d	1.875	0.439	2.685	1.225	2.854	2.459	2.367	0.932	1.387	2.004	3.420	2.721	2.357	3.282

master branch:

commit	astar	copy_and_run	coremark	gcc	gromacs	lbm	linux	mcf	microbench	milc	namd	povray	wrf	xalancbmk
a6696f0
c092d57
0ae34b3
042e89e	1.952	0.439	2.696	1.228	2.847	2.457	2.366	0.933	1.400	1.979	3.418	2.726	2.383	3.272
729ce9e	1.952	0.439	2.696	1.228	2.847	2.457	2.366	0.933	1.400	1.979	3.418	2.726	2.383	3.272