check_chassis_brocade.pl: add --perf option

Add --perf option to produce performance data output
Output example:
OK - CPU: 1min 1% 5sec 1% 1sec 1%. Memory OK (6%). Temp (A/W/C): 48.5/85.0/90.0; Fans: OK OK. PSUs: OK N/A. Up 25.91 days|CPU_1min=1%;70;90 CPU_5sec=1%;85;95 CPU_1sec=1%;95;98 Memory=6%;70;90 Temp=48.5deg;85.0;90.0