firmware: arm_ffa: Fix sched-recv callback partition lookup

firmware: arm_ffa: Fix sched-recv callback partition lookup

ffa_sched_recv_cb_update() used list_for_each_entry_safe() to search for
a matching partition and then tested the iterator against NULL. That is
not a valid end-of-list check for circular lists and can fall through
with an invalid pointer. Use a normal iterator and detect the not-found
case correctly before touching the partition state.

Fixes: be61da938576 ("firmware: arm_ffa: Allow multiple UUIDs per partition to register SRI callback")
Link: https://patch.msgid.link/20260428-ffa_fixes-v2-11-8595ae450034@kernel.org
Signed-off-by: Sudeep Holla <sudeep.holla@kernel.org>