staging:rtl8192u: Rename member variables - Style

Rename the member variables FragNum and SeqNum. This change clears
a checkpatch issue with CamelCase naming.

This is 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>