common: Move sorting functions to their own header file

These don't need to be in common.h so move them out into a new header.
Also add some missing comments.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Tom Rini <trini@konsulko.com>

include/sort.h

@@ -0,0 +1,34 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+/*
+ * Copyright 2019 Google LLC
+ */
+
+#ifndef __SORT_H
+#define __SORT_H
+
+/**
+ * qsort() - Use the quicksort algorithm to sort some values
+ *
+ * @base: Base address of array to sort
+ * @nmemb: Number of members to sort
+ * @size: Size of each member in bytes
+ * @compar: Comparison function which should return:
+ *	< 0 if element at s1 < element at s2,
+ *	  0 if element at s1 == element at s2,
+ *	> 0 if element at s1 > element at s2,
+ */
+void qsort(void *base, size_t nmemb, size_t size,
+	   int (*compar)(const void *s1, const void *s2));
+
+/**
+ * strcmp_compar() - compar function for string arrays
+ *
+ * This can be passed to qsort when a string array is being sorted
+ *
+ * @s1: First string to compare
+ * @s2: Second string to compare
+ * @return comparison value (less than, equal to, or greater than 0)
+ */
+int strcmp_compar(const void *s1, const void *s2);
+
+#endif