coupledL2, L2Top, XSTile: refactor CoupledL2 top-level framework

[linjuanZ]

• backbone: refactor CoupledL2 top-level framework

TL2TLCoupledL2 and TL2CHICoupledL2 used to flatten all the logics in each top-level module, which makes two versions of CoupledL2 repeat lots of the logics. In fact, these two versions share most of the logics in the top level except for outer interface (one for TileLink and one for CHI).

This commit extracts the common parts between TileLink and CHI and modularizes into CoupledL2, so that TL2TLCoupledL2 and TL2CHICoupledL2 only need to implement the differences with each other.

• MMIOBridge: fix address range for MMIO address space

[XiangShanRobot]

[Generated by IPC robot] commit: 086bc9f983aa9f781a0c82643abf3e3c683a3f73	commit	astar	copy_and_run	coremark	gcc	gromacs	lbm	linux	mcf	microbench	milc	namd	povray	wrf	xalancbmk
086bc9f	1.868	0.448	2.096	1.166	2.945	2.603	2.333	0.952	1.377	1.298	3.424	2.659	2.468	2.945

master branch:	commit	astar	copy_and_run	coremark	gcc	gromacs	lbm	linux	mcf	microbench	milc	namd	povray	wrf	xalancbmk
df7130a	1.823	0.448	2.054	1.172	2.950	2.500	2.292	0.923	1.376	1.265	3.449	2.656	2.398	2.943
b51ac1c	1.823	0.448	2.054	1.172	2.950	2.500	2.292	0.923	1.376	1.265	3.449	2.656	2.398	2.943
79fadd7	1.868	0.448	2.096	1.166	2.945	2.603	2.333	0.952	1.377	1.298	3.424	2.659	2.468	2.945
f48d8a2	1.868	0.448	2.096	1.166	2.945	2.603	2.333	0.952	1.377	1.298	3.424	2.659	2.468	2.945
4ccb2e8	1.868		2.096	1.166	2.945	2.603	2.333	0.951	1.377	1.298	3.424		2.468	2.945
453674e	1.861	0.448	2.096	1.190	2.933	2.600	2.335	0.954	1.377	1.353	3.437	2.667	2.467	2.943
f6458cc	1.861	0.448	2.096	1.190	2.933	2.600	2.335	0.954	1.377	1.353	3.437	2.667	2.467	2.943
adf98a9	1.861	0.448	2.096	1.190	2.933	2.600	2.335	0.954	1.377	1.353	3.437	2.667	2.467	2.943
fcd66f1	1.861		2.096	1.190	2.933	2.600	2.335	0.954	1.377	1.353	3.437	2.667	2.467	2.943
8702944	1.861	0.448	2.096	1.190	2.933	2.600	2.335	0.954	1.377	1.353	3.437	2.667	2.467	2.943