Addressed void* return warning in all keymaps

keyboard/atreus/atreus.c

@@ -1,16 +1,16 @@
 #include "atreus.h"
 
 __attribute__ ((weak))
-void * matrix_init_user(void) {
+void matrix_init_user(void) {
 	// leave these blank
 };
 
 __attribute__ ((weak))
-void * matrix_scan_user(void) {
+void matrix_scan_user(void) {
 	// leave these blank
 };
 
-void * matrix_init_kb(void) {
+void matrix_init_kb(void) {
 	// put your keyboard start-up code here
 	// runs once when the firmware starts up
 
@@ -19,7 +19,7 @@ void * matrix_init_kb(void) {
 	}
 };
 
-void * matrix_scan_kb(void) {
+void matrix_scan_kb(void) {
 	// put your looping keyboard code here
 	// runs every cycle (a lot)
 

keyboard/atreus/atreus.h

@@ -22,7 +22,7 @@
 	{ k2a, k30, k31, k32, k33, k34,   k36, k37, k38, k39, k3a } \
 }
 
-void * matrix_init_user(void);
-void * matrix_scan_user(void);
+void matrix_init_user(void);
+void matrix_scan_user(void);
 
 #endif