Merge pull request #2180 from thinkyhead/fix_radian

Fix DEGREES macro

Marlin/Marlin.h

 #define TEST(n,b) (((n)&BIT(b))!=0)
 #define SET_BIT(n,b,value) (n) ^= ((-value)^(n)) & (BIT(b))
 #define RADIANS(d) ((d)*M_PI/180.0)
-#define DEGREES(r) ((d)*180.0/M_PI)
+#define DEGREES(r) ((r)*180.0/M_PI)
 #define NOLESS(v,n) do{ if (v < n) v = n; }while(0)
 #define NOMORE(v,n) do{ if (v > n) v = n; }while(0)