cc: fix spurious warning on comparsion with scope redeclared variable (thanks aiju)

> warning: a.c:9 useless or misleading comparison: UINT < 0

the error can be observed by compiling the following code
with warnings enabled:

#include <u.h>
#include <libc.h>

uint r;

void
main(int argc, char *argv[])
{
	int r;

	if(r < 0){
		exits(0);
	}
}

the offending code in the compiler is:

-	if(l->op == ONAME && l->sym->type){
-		lt = l->sym->type;
-		if(lt->etype == TARRAY)
-			lt = lt->link;
-	}

compiler handles scope by overwritin and reverting
symbols while parsing. in the ccom phase, the nodes symbol
(n->sym) is not in the right scope and we wrongly think r
is uint instead of int.

it is not clear to me what this code tried to accomplish in
the first place nor could anyone answer me this question.

the risk is small as this change doesnt affect the compiled
program, only the warning, so removing the offending code.

sys/src/cmd/cc/com.c

@@ -1370,11 +1370,6 @@ compar(Node *n, int reverse)
 	if(l->op == OCONST)
 		return 0;
 	lt = l->type;
-	if(l->op == ONAME && l->sym->type){
-		lt = l->sym->type;
-		if(lt->etype == TARRAY)
-			lt = lt->link;
-	}
 	if(lt == T)
 		return 0;
 	if(lt->etype == TXXX || lt->etype > TUVLONG)