Remove using namespace

It is against the coding standard, and could lead to conflicts
in the future.
Explicitly declare the objects being used with using.

Change-Id: I931488490ae306282a7288b9533fe2745ad7b89f
Signed-off-by: Ed Tanous <ed@tanous.net>
diff --git a/ssifbridged.cpp b/ssifbridged.cpp
index 5ac0eed..2752102 100644
--- a/ssifbridged.cpp
+++ b/ssifbridged.cpp
@@ -37,7 +37,8 @@
 /* Max length of ipmi ssif message included netfn and cmd field */
 #define IPMI_SSIF_PAYLOAD_MAX 254
 
-using namespace phosphor::logging;
+using phosphor::logging::level;
+using phosphor::logging::log;
 
 struct ipmi_cmd
 {