firmware: arm_ffa: Check for NULL FF-A ID table while driver registration

firmware: arm_ffa: Check for NULL FF-A ID table while driver registration

The bus match callback assumes that every FF-A driver provides an
id_table and dereferences it unconditionally. Enforce that contract at
registration time so a buggy client driver cannot crash the bus during
match.

Fixes: 92743071464f ("firmware: arm_ffa: Ensure drivers provide a probe function")
Link: https://patch.msgid.link/20260428-ffa_fixes-v2-1-8595ae450034@kernel.org
Signed-off-by: Sudeep Holla <sudeep.holla@kernel.org>