kernel: Remove some unused macros.

Spotted by Clang. (I double-checked they weren't used within
some #ifdef'd-out code, too.)

src/system/kernel/debug/debug.cpp

@@ -153,9 +153,6 @@ static int32 sHandOverKDLToCPU = -1;
 static bool sCPUTrapped[SMP_MAX_CPUS];
 
 
-#define distance(a, b) ((a) < (b) ? (b) - (a) : (a) - (b))
-
-
 // #pragma mark - DebugOutputFilter
 
 

src/system/kernel/disk_device_manager/KFileDiskDevice.cpp

@@ -19,12 +19,6 @@
 #include <KPath.h>
 
 
-// debugging
-//#define DBG(x)
-#define DBG(x) x
-#define OUT dprintf
-
-
 static const char* kFileDevicesDir = "/dev/disk/virtual/files";