Simplify arena_alloc implementation

arena.h

@@ -84,13 +84,8 @@ void *arena_alloc(Arena *a, size_t bytes)
             a->tail = a->tail->next;
         }
 
-        // If found allocate on that region
-        if (bytes <= a->tail->capacity - a->tail->count) {
-            a->tail->count += bytes;
-            return a->tail->data + a->tail->count;
-        }
-
-        // If not create a new region
+        // If not found create a new region
+        if (bytes > a->tail->capacity - a->tail->count) {
             size_t size = (bytes > region_capacity ? bytes : region_capacity);
             a->tail->next = (Arena_Region*)ARENA_REALLOC(NULL, sizeof(*a->tail) + size);
             ARENA_ASSERT(a->head != NULL);
@@ -102,6 +97,7 @@ void *arena_alloc(Arena *a, size_t bytes)
             a->tail->capacity = size;
             return a->tail->data;
         }
+    }
 
     a->tail->count += bytes;
     return a->tail->data + a->tail->count;