include/string: Add strrchr

Copy strrchr from libpayload.
To be used by Cavium's BDK or FDT parsers.

Change-Id: Iab7981c25113ed16f1b8130de4935d30c29d2fa5
Signed-off-by: Patrick Rudolph <patrick.rudolph@9elements.com>
Reviewed-on: https://review.coreboot.org/25447
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: David Hendricks <david.hendricks@gmail.com>

src/include/string.h

@@ -66,6 +66,26 @@ static inline char *strconcat(const char *s1, const char *s2)
 }
 #endif
 
+/**
+ * Find a character in a string.
+ *
+ * @param s The string.
+ * @param c The character.
+ * @return A pointer to the last occurrence of the character in the
+ * string, or NULL if the character was not encountered within the string.
+ */
+static inline char *strrchr(const char *s, int c)
+{
+	char *p = (char *)s + strlen(s);
+
+	for (; p >= s; p--) {
+		if (*p == c)
+			return p;
+	}
+
+	return NULL;
+}
+
 static inline char *strncpy(char *to, const char *from, int count)
 {
 	register char *ret = to;