staging: rtl8712: r8712_append_mpdu_unit(): Change return type

Change return type of r8712_append_mpdu_unit from u8 to void and remove
its return statement as it always returns only _SUCCESS. Modify call
sites to simply call this function instead of checking its return value,
and execute all the statements in the if-block for when the function
returns _SUCCESS.

Signed-off-by: Nishka Dasgupta <nishkadg.linux@gmail.com>
Link: https://lore.kernel.org/r/20190813044638.16348-2-nishkadg.linux@gmail.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>