lmb: Rename free_mem to available_mem

free_mem is a misnomer. We never update it with the free memory for
LMB. Instead, it describes all available memory and is checked against
used_mem to decide whether an area is free or not.

So let's rename this field to better match its usage.

Reviewed-by: Sam Protsenko <semen.protsenko@linaro.org>
Tested-by: Sam Protsenko <semen.protsenko@linaro.org>
Signed-off-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
diff --git a/test/cmd/bdinfo.c b/test/cmd/bdinfo.c
index 014391b..7642948 100644
--- a/test/cmd/bdinfo.c
+++ b/test/cmd/bdinfo.c
@@ -131,7 +131,7 @@
 	struct lmb *lmb = lmb_get();
 
 	ut_assert_nextline("lmb_dump_all:");
-	ut_assertok(lmb_test_dump_region(uts, &lmb->free_mem, "memory"));
+	ut_assertok(lmb_test_dump_region(uts, &lmb->available_mem, "memory"));
 	ut_assertok(lmb_test_dump_region(uts, &lmb->used_mem, "reserved"));
 
 	return 0;