Update FI9821W_Y2k.pm

Fixed this issue:
"my" variable $cmd masks earlier declaration in same scope at FI9821W_Y2k.pm line 138.
"my" variable $cmd masks earlier declaration in same scope at FI9821W_Y2k.pm line 141.
"my" variable $cmd masks earlier declaration in same scope at FI9821W_Y2k.pm line 144.
"my" variable $cmd masks earlier declaration in same scope at FI9821W_Y2k.pm line 154.
"my" variable $cmd masks earlier declaration in same scope at FI9821W_Y2k.pm line 156.
"my" variable $cmd masks earlier declaration in same scope at FI9821W_Y2k.pm line 195.
"my" variable $cmd masks earlier declaration in same scope at FI9821W_Y2k.pm line 222.
"my" variable $cmd masks earlier declaration in same scope at FI9821W_Y2k.pm line 247.
"my" variable $cmd masks earlier declaration in same scope at FI9821W_Y2k.pm line 275.
"my" variable $cmd masks earlier declaration in same scope at FI9821W_Y2k.pm line 302.
"my" variable $cmd masks earlier declaration in same scope at FI9821W_Y2k.pm line 329.
"my" variable $cmd masks earlier declaration in same scope at FI9821W_Y2k.pm line 356.
"my" variable $cmd masks earlier declaration in same scope at FI9821W_Y2k.pm line 383.
"my" variable $cmd masks earlier declaration in same scope at FI9821W_Y2k.pm line 399.
"my" variable $cmd masks earlier declaration in same scope at FI9821W_Y2k.pm line 414.
"my" variable $cmd masks earlier declaration in same scope at FI9821W_Y2k.pm line 448.
"my" variable $cmd masks earlier declaration in same scope at FI9821W_Y2k.pm line 671.
"my" variable $cmd masks earlier declaration in same scope at FI9821W_Y2k.pm line 690.
Merge pull request #485 from florian-asche/patch-1

Update FI9821W_Y2k.pm