staging:rtl8192u: Refactor SEQUENCE_CONTROL - Style

Remove the 'typedef' from union SEQUENCE_CONTROL. This clears a
checkpatch issue with defining new types.

Additionally renamed the union to lowercase to comply with coding
standard.

These are coding style changes which should not impact runtime
code execution.

typedef union _SEQUENCE_CONTROL{
+union sequence_control {

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