[NTOS:CM] Implement COMPUTE_HASH_CHAR macro definition

Wrap the hash computation formula in a macro so that we don't have to copy
the logic over the places again and again.

ntoskrnl/include/internal/cm_x.h

@@ -12,6 +12,12 @@
 #define GET_HASH_KEY(ConvKey)                                       \
     ((CMP_HASH_IRRATIONAL * (ConvKey)) % CMP_HASH_PRIME)
 
+//
+// Computes the hashkey of a character
+//
+#define COMPUTE_HASH_CHAR(ConvKey, Char)                            \
+    (37 * ConvKey + RtlUpcaseUnicodeChar(Char))
+
 //
 // Returns the index into the hash table, or the entry itself
 //