lib/gcd: add kernel-doc notation

Add kernel-doc notation for the gcd() function (so that it can be
added to the kernel-api documentation).
Signed-off-by: NRandy Dunlap <rdunlap@infradead.org>
Signed-off-by: NJonathan Corbet <corbet@lwn.net>

lib/gcd.c

@@ -13,6 +13,12 @@
 #if !defined(CONFIG_CPU_NO_EFFICIENT_FFS) && !defined(CPU_NO_EFFICIENT_FFS)
 
 /* If __ffs is available, the even/odd algorithm benchmarks slower. */
+
+/**
+ * gcd - calculate and return the greatest common divisor of 2 unsigned longs
+ * @a: first value
+ * @b: second value
+ */
 unsigned long gcd(unsigned long a, unsigned long b)
 {
 	unsigned long r = a | b;