From Colus Tang via https://bugs.wireshark.org/bugzilla/show_bug.cgi?id=7134

From Colus Tang via https://bugs.wireshark.org/bugzilla/show_bug.cgi?id=7134
Unable to display the correct IEEE802.11 MCS data rates due to header definition

The problem is due to the ieee_802_11_phdr.data_rate is defined as guint8,
since this variable is counting number of 0.5Mbps units, any datarates which is
higher than 255Mbps would get wrapped up.  In the above example, only the lower
8bit value will be put into the ieee_802_11_phdr which is 0x04 and result in
the incorrect 2Mbps display.

There are 802.11n WLAN product is capable to transmit @450Mbps, we should fix
this data_rate from guint8 to guint16.

#BACKPORT

svn path=/trunk/; revision=42123