[libc][NFC] Remove DEFAULT_DOUBLE_SPLIT macro. (#126822)

Author: lntue

libc/src/__support/FPUtil/double_double.h

@@ -18,14 +18,12 @@
 namespace LIBC_NAMESPACE_DECL {
 namespace fputil {
 
-#define DEFAULT_DOUBLE_SPLIT 27
-
 template <typename T> struct DefaultSplit;
 template <> struct DefaultSplit<float> {
   static constexpr size_t VALUE = 12;
 };
 template <> struct DefaultSplit<double> {
-  static constexpr size_t VALUE = DEFAULT_DOUBLE_SPLIT;
+  static constexpr size_t VALUE = 27;
 };
 
 using DoubleDouble = NumberPair<double>;

libc/src/math/generic/range_reduction_double_common.h

@@ -21,7 +21,7 @@
 namespace LIBC_NAMESPACE_DECL {
 
 #ifdef LIBC_TARGET_CPU_HAS_FMA
-static constexpr unsigned SPLIT = DEFAULT_DOUBLE_SPLIT;
+static constexpr unsigned SPLIT = fputil::DefaultSplit<double>::VALUE;
 #else
 // When there is no-FMA instructions, in order to have exact product of 2 double
 // precision with directional roundings, we need to lower the precision of the