Fix amd64-gcc build by removing declarations already in amd64/include/counter.h
Error messages:
/workspace/src/sys/amd64/amd64/pmap.c:446:21: error: redundant redeclaration of '__pcpu' [-Werror=redundant-decls] extern struct pcpu *__pcpu; ^~~~~~ In file included from /workspace/src/sys/sys/counter.h:37:0, from /workspace/src/sys/sys/vmmeter.h:65, from /workspace/src/sys/amd64/amd64/pmap.c:130: ./machine/counter.h:36:21: note: previous declaration of '__pcpu' was here extern struct pcpu *__pcpu;
/workspace/src/sys/amd64/amd64/pmap.c:447:20: error: redundant redeclaration of 'temp_bsp_pcpu' [-Werror=redundant-decls] extern struct pcpu temp_bsp_pcpu; ^~~~~~~~~~~~~ In file included from /workspace/src/sys/sys/counter.h:37:0, from /workspace/src/sys/sys/vmmeter.h:65, from /workspace/src/sys/amd64/amd64/pmap.c:130: ./machine/counter.h:37:20: note: previous declaration of 'temp_bsp_pcpu' was here extern struct pcpu temp_bsp_pcpu; ^~~~~~~~~~~~~