chore: fix code review comments

Rename setup_and_discovery.c in services to discovery.c per [1]. File
really only does discovery and no setup related to FF-A.

Improve readability per comment in [2].

[1]https://review.trustedfirmware.org/c/hafnium/hafnium/+/18570/comment/075ead89_89f65914/
[2]
https://review.trustedfirmware.org/c/hafnium/hafnium/+/18566/comment/0203e100_79f07ee5/

Signed-off-by: Raghu Krishnamurthy <raghu.ncstate@gmail.com>
Change-Id: I04c82c8bed26f4c90d3f41300c06e08e41d8b848
diff --git a/inc/hf/std.h b/inc/hf/std.h
index 3e37c3a..ca540e1 100644
--- a/inc/hf/std.h
+++ b/inc/hf/std.h
@@ -10,6 +10,9 @@
 
 #include "hf/arch/std.h"
 
+#define MAX(x, y) (x > y ? x : y)
+#define MIN(x, y) (x < y ? x : y)
+
 typedef size_t rsize_t;
 
 /**