staging: lustre: restore initialization of return code

A recent rework dropped the initialization of the initialization of the
successful return code in lov_getstripe:

drivers/staging/lustre/lustre/lov/lov_pack.c: In function 'lov_getstripe':
drivers/staging/lustre/lustre/lov/lov_pack.c:426:9: error: 'rc' may be used uninitialized in this function [-Werror=maybe-uninitialized]
drivers/staging/lustre/lustre/lov/lov_pack.c:313:6: note: 'rc' was declared here

This adds it back.

Fixes: e10a431b ("staging: lustre: lov: move LSM to LOV layer")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>