Fix litedram wrapper build warnings and metavalues

Fix litedram wrapper build warnings and metavalues

This fixes a couple of build warnings in litedram-wrapper-l2.vhdl

litedram/extras/litedram-wrapper-l2.vhdl:552:17:warning: declaration of "i" hides constant "i" [-Whide]
            for i in 0 to ROW_SIZE-1 loop
                ^
litedram/extras/litedram-wrapper-l2.vhdl:1129:9:warning: declaration of "litedram_trace" hides generic "litedram_trace" [-Whide]
        litedram_trace: litedram_trace_stub;
        ^

It also cleans up the runtime metavalue warnings

Signed-off-by: Michael Neuling <mikey@neuling.org>