gnrc_mac: fix header includes

The inclusion of `net/gnrc.h` in `net/gnrc/mac/types.h` header makes it
impossible to include the `net/gnrc/netif.h` header within
`net/gnrc/netif/hdr.h`, due to `net/gnrc/mac/types.h` being included
with `net/gnrc/netif/mac.h` (which is included in `net/gnrc/netif.h`)

sys/include/net/gnrc/gomach/types.h

@@ -24,7 +24,6 @@
 
 #include "kernel_types.h"
 #include "xtimer.h"
-#include "net/gnrc.h"
 #include "net/gnrc/gomach/hdr.h"
 
 #ifdef __cplusplus

sys/include/net/gnrc/mac/types.h

@@ -25,7 +25,7 @@
 #include <stdbool.h>
 
 #include "kernel_types.h"
-#include "net/gnrc.h"
+#include "net/gnrc/pkt.h"
 #include "net/gnrc/priority_pktqueue.h"
 #include "net/ieee802154.h"
 #include "net/gnrc/mac/mac.h"

sys/net/gnrc/link_layer/lwmac/lwmac.c

@@ -29,6 +29,7 @@
 #include "random.h"
 #include "periph/rtt.h"
 #include "net/gnrc/netif.h"
+#include "net/gnrc/netif/hdr.h"
 #include "net/gnrc/netif/internal.h"
 #include "net/gnrc/netif/ieee802154.h"
 #include "net/netdev/ieee802154.h"

tests/unittests/tests-gnrc_mac_internal/tests-gnrc_mac_internal.c

@@ -15,7 +15,8 @@
 
 #include "embUnit.h"
 
-#include "net/gnrc/pkt.h"
+#include "net/gnrc/pktbuf.h"
+#include "net/gnrc/netif/hdr.h"
 #include "net/gnrc/mac/internal.h"
 
 #include "unittests-constants.h"