Use api.hpp instead of api.h

Since the api.h file has been gradually deprecated, this submission
will use api.hpp instead of api.h

Change-Id: Ic9c8ebe0ba96b0a11b9415cd52acdf58fe9d828e
Signed-off-by: George Liu <liuxiwei@ieisystem.com>
Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
diff --git a/ipmi/control.hpp b/ipmi/control.hpp
index 4f1f0ad..2f57e99 100644
--- a/ipmi/control.hpp
+++ b/ipmi/control.hpp
@@ -3,9 +3,7 @@
 #include <cstdint>
 #include <string>
 
-namespace pid_control
-{
-namespace ipmi
+namespace pid_control::ipmi
 {
 
 // Implement this interface to control a zone's mode or read back its status.
@@ -25,5 +23,4 @@
                                        const std::string& property) = 0;
 };
 
-} // namespace ipmi
-} // namespace pid_control
+} // namespace pid_control::ipmi