staging: rtl8712: r8712_wlanhdr_to_ethhdr(): Change return values

Change return values of r8712_wlanhdr_to_ethhdr from _SUCCESS/_FAIL to
0/-ENOMEM. Modify the function containing a call site of
r8712_wlanhdr_to_ethhdr so that it compares the return value to
0/-ENOMEM instead of _SUCCESS/_FAIL.
Change the return type of r8712_wlanhdr_to_ethhdr from sint to int to
match its prototype in corresponding .h file.

Signed-off-by: Nishka Dasgupta <nishkadg.linux@gmail.com>
Link: https://lore.kernel.org/r/20190808064012.12661-3-nishkadg.linux@gmail.com


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