sparc: perf: Remove redundant perf_pmu_{en|dis}able calls

perf_pmu_disable is called by core perf code before pmu->del and the
enable function is called by core perf code afterwards. No need to
call again within sparc_pmu_del.

Ditto for pmu->add and sparc_pmu_add.

Signed-off-by: David Ahern <david.ahern@oracle.com>
Acked-by: Bob Picco <bob.picco@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>