misc: fastrpc: Remove kernel-side domain checks from capability ioctl

misc: fastrpc: Remove kernel-side domain checks from capability ioctl

Domain ID in the uAPI is misleading. Remove checks and log messages
related to 'domain' field in capability structure. Update UAPI to
mark the field as unused.

Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
Reviewed-by: Ekansh Gupta <ekansh.gupta@oss.qualcomm.com>
Signed-off-by: Ling Xu <quic_lxu5@quicinc.com>
Signed-off-by: Srinivas Kandagatla <srini@kernel.org>
Link: https://lore.kernel.org/r/20250912131302.303199-3-srini@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>