staging: rtl8712: amsdu_to_msdu(): Change return type

Change return type of amsdu_to_msdu from int to void as it always
returns _SUCCESS. Remove return statement as well.
As this return value was never anything other than _SUCCESS, remove the
if-branch that depends on the return value not being _SUCCESS.
Remove local variable that was only used in the now-removed if-branch
Modify call site to call the function amsdu_to_msdu without expecting
a return value.

Signed-off-by: Nishka Dasgupta <nishkadg.linux@gmail.com>
Link: https://lore.kernel.org/r/20190808064012.12661-1-nishkadg.linux@gmail.com


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