amt: fix wrong return type of amt_send_membership_update()

amt_send_membership_update() would return -1 but it's return type is bool.
So, it should be used TRUE instead of -1.

Fixes: cbc21dc1 ("amt: add data plane of amt interface")
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Taehee Yoo <ap420073@gmail.com>
Link: https://lore.kernel.org/r/20220109163702.6331-1-ap420073@gmail.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>