fix(PTW): clear reg after resp to prevent problem

[cebarobot]

PTW use reg full_gvpn_reg to generate GPF for out-of-range gpaddr, but this reg is not cleared after PTW response. If the last PTW request got a bad full_gvpn_reg, the gvpn_gpf and guestFault keeps until next PTW request, resulting in the total mess of state machine.

This patch clears full_gvpn_reg at the response of PTW. As PTW could response in two state paths, this patch adds an independent condition to achieve this.

[XiangShanRobot]

[Generated by IPC robot]
commit: 0d651ad

commit	astar	copy_and_run	coremark	gcc	gromacs	lbm	linux	mcf	microbench	milc	namd	povray	wrf	xalancbmk
0d651ad	1.837	0.442	2.640	1.211	2.154	2.142	2.364	0.941	1.402	1.908	3.110	2.554	2.276	3.311

master branch:

commit	astar	copy_and_run	coremark	gcc	gromacs	lbm	linux	mcf	microbench	milc	namd	povray	wrf	xalancbmk
066ca24	1.834	0.442	2.640	1.211	2.154	2.142	2.364	0.941	1.402	1.908	3.110	2.554	2.276	3.311
6aee9d0	1.837	0.442	2.640	1.211	2.154	2.142	2.364	0.941	1.402	1.908	3.110	2.554	2.276	3.311
75ed9f4	1.837	0.442	2.640	1.211	2.154	2.142	2.364	0.941	1.399	1.908	3.110	2.554	2.276	3.311
748214a	1.834	0.442	2.640	1.211	2.154	2.142	2.364	0.941	1.402	1.908	3.110	2.551	2.276	3.311
4863970	1.811	0.442	2.640	1.211	2.154	2.143	2.363	0.952	1.402	1.908	3.110	2.555	2.278	3.311