Currently if the dot11_mode is set to eCSR_DOT11_MODE_11g or
eCSR_DOT11_MODE_11g_ONLY and a channel switch is triggered with
target channel in 5Ghz band, then an invalid combination of dot11_mode
and channel occurs which fails the vdev_restart for channel switch.
Update the dot11_mode based on the target channel and the current
dot11_mode before sending the channel change request to SME.
Change-Id: I2b0fa4a36f137150ee0506d62be29ede4f4e604c
CRs-Fixed: 2276876