fix m68k float.h long double exponent range

unlike the x86 variant, the m68k ld80 format allows (biased) exponent
zero with mantissa msb set, thereby extending the normal range.

arch/m68k/bits/float.h

@@ -3,12 +3,12 @@
 #define FLT_EVAL_METHOD 2
 
 #define LDBL_TRUE_MIN 3.6451995318824746025e-4951L
-#define LDBL_MIN     3.3621031431120935063e-4932L
+#define LDBL_MIN     1.68105157155604675313e-4932L
 #define LDBL_MAX     1.1897314953572317650e+4932L
 #define LDBL_EPSILON 1.0842021724855044340e-19L
 
 #define LDBL_MANT_DIG 64
-#define LDBL_MIN_EXP (-16381)
+#define LDBL_MIN_EXP (-16382)
 #define LDBL_MAX_EXP 16384
 
 #define LDBL_DIG 18