bpu: remove most reset signals of SRAMs

[Lingrui98]

Try to test mmio mechanisms. If there are no problems, then we can save a mux on critical paths of sram read and write.

[poemonsense]

[Generated by IPC robot] commit: 11e2acb043ed83d35793db0c160bdfeb1b11143a

commit	astar	copy_and_run	coremark	gcc	gromacs	lbm	linux	mcf	microbench	milc	namd	povray	wrf	xalancbmk
11e2acb	1.427	0.506	1.965	1.051	2.503	1.432	1.275	0.351	1.287	0.949	3.231	2.369	2.152	1.627

master branch:

commit	astar	copy_and_run	coremark	gcc	gromacs	lbm	linux	mcf	microbench	milc	namd	povray	wrf	xalancbmk
d298fe6	1.430	0.517	1.984	1.063	2.510	1.434	1.284	0.349	1.307	0.954	3.278	2.435	2.156	1.629
6786cfb	1.435	0.516	2.004	1.061	2.513	1.435	1.287	0.349	1.346	0.953	3.285	2.427	2.157	1.629
fa9d712	1.433	0.516	2.004	1.061	2.513	1.435	1.287	0.349	1.327	0.953	3.280	2.437	2.155	1.629
92816bb	1.433	0.520	1.996	1.064	2.541	1.441	1.303	0.350	1.384	0.957	3.285	2.463	2.166	1.598
7a5caa9	1.442	0.520	1.996	1.064	2.534	1.442	1.305	0.349	1.351	0.957	3.304	2.457	2.167	1.582
fa9f969	1.442	0.520	1.996	1.064	2.534	1.442	1.304	0.350	1.351	0.957	3.307	2.470	2.165	1.582
6c4dcc2	1.442	0.520	1.996	1.064	2.534	1.442	1.305	0.348	1.347	0.957	3.306	2.453	2.164	1.582
445d5c0	1.433	0.520	1.996	1.065	2.533	1.441	1.299	0.351	1.351	0.950	3.301	2.458	2.167	1.577
5ef86c3	1.435	0.520	1.996	1.065	2.533	1.441	1.306	0.350	1.351	0.950	3.298	2.469	2.160	1.577
b54c2fd	1.432	0.520	1.996	1.064	2.533	1.441	1.302	0.350	1.347	0.950	3.295	2.477	2.167	1.577