move round_up() into mnode_math

include/mesytec-mnode/mnode_math.h

@@ -0,0 +1,18 @@
+#ifndef C536E080_25D7_476D_B8E3_25912B9CFC3B
+#define C536E080_25D7_476D_B8E3_25912B9CFC3B
+
+#include <cstdint>
+
+namespace mesytec::mnode
+{
+// round n up to the nearest multiple of p
+// source: https://blog.xoria.org/rounding-up/
+inline int64_t round_up(int64_t n, int64_t p)
+{
+    int64_t mask = p - 1;
+    return (n + mask) & ~mask;
+}
+
+}
+
+#endif /* C536E080_25D7_476D_B8E3_25912B9CFC3B */