You can only access for-generate instances with constants. You can do that with another for-generate loop.
property sram(index);
@(posedge clk) disable iff(!resetn)
bank_sel == index &&
sram_top.u_0.sram_col_inst[index].sram_row.cen[sram_sel]
|->
…
endproperty
for(genvar i=0;i<MAX_SEL;i++) begin : bank
assert property(sram(i));
end