Revert "[LV] Re-use existing broadcast value for live-ins."

This reverts commit eea92586.

That commit triggered crashes in the following testcase:

$ cat reduced.c
typedef struct {
  int a[8]
} b;
typedef struct {
  b *c;
  short d
} e;
void f() {
  int g;
  char *h;
  e *i = f;
  short j = i->d;
  int a = i->c->a[0];
  for (;;)
    for (; g < a; g++) {
      *h = j * i->d >> 8;
      h++;
    }
}
$ clang -target aarch64-linux-gnu -w -c -O2 reduced.c