Within a module, Verilog contains essentially two constructs: items and statements. Statements are always found in procedural contexts, which include anything in between begin..end, functions, tasks, always blocks and initial blocks. Items, such as generate constructs, are listed directly in the module. For loops and most variable/constant declarations can exist in both contexts.
In your code, it appears that you want the for loop to be evaluated as a generate item but the loop is actually part of the procedural context of the always block. For a for loop to be treated as a generate loop it must be in the module context. The generate..endgenerate keywords are entirely optional(some tools require them) and have no effect. See this answer for an example of how generate loops are evaluated.
//Compiler sees this
parameter ROWBITS = 4;
reg [ROWBITS-1:0] temp;
genvar c;
always @(posedge sysclk) //Procedural context starts here
begin
for (c = 0; c < ROWBITS; c = c + 1) begin: test
temp[c] <= 1'b0; //Still a genvar
end
end