staging:rtl8192u: Rename SwChnlCmd - Style

Rename the structure SwChnlCmd to sw_chnl_cmd. This change clears the
checkpatch issue with CamelCase naming. The change is purely a coding
style change and should have no impact on runtime code execution.

Signed-off-by: John Whitmore <johnfwhitmore@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>