[IGMP]: Fix IGMPV3_EXP() normalization bit shift value.

The IGMPV3_EXP() macro doesn't correctly shift the normalization bit, so
time-out values are longer than they should be.

Thanks to Dirk Ooms for finding the problem in IGMPv3 - MLDv2 had a
similar problem that was already fixed a year ago. :-(
Signed-off-by: David L Stevens <dlstevens@us.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/igmp.h

@@ -191,7 +191,7 @@ struct ip_mc_list
 #define IGMPV3_MASK(value, nb) ((nb)>=32 ? (value) : ((1<<(nb))-1) & (value))
 #define IGMPV3_EXP(thresh, nbmant, nbexp, value) \
 	((value) < (thresh) ? (value) : \
-        ((IGMPV3_MASK(value, nbmant) | (1<<(nbmant+nbexp))) << \
+        ((IGMPV3_MASK(value, nbmant) | (1<<(nbmant))) << \
          (IGMPV3_MASK((value) >> (nbmant), nbexp) + (nbexp))))
 
 #define IGMPV3_QQIC(value) IGMPV3_EXP(0x80, 4, 3, value)