media: cec/core: clarify rx-arb-lost usage message

The rx-arb-lost error injection command only works with <op> set to 'any'.
Explicitly say so in the usage message.

Also use [] to indicate that the <poll> argument is optional.
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>

Documentation/userspace-api/media/cec/cec-pin-error-inj.rst

@@ -44,7 +44,7 @@ error injection status::
 	#   <op>[,<mode>] rx-low-drive <bit>   force a low-drive condition at this bit position
 	#   <op>[,<mode>] rx-add-byte          add a spurious byte to the received CEC message
 	#   <op>[,<mode>] rx-remove-byte       remove the last byte from the received CEC message
-	#   <op>[,<mode>] rx-arb-lost <poll>   generate a POLL message to trigger an arbitration lost
+	#    any[,<mode>] rx-arb-lost [<poll>] generate a POLL message to trigger an arbitration lost
 	#
 	# TX error injection settings:
 	#   tx-ignore-nack-until-eom           ignore early NACKs until EOM

drivers/media/cec/core/cec-pin-error-inj.c

@@ -277,7 +277,7 @@ int cec_pin_error_inj_show(struct cec_adapter *adap, struct seq_file *sf)
 	seq_puts(sf, "#   <op>[,<mode>] rx-low-drive <bit>   force a low-drive condition at this bit position\n");
 	seq_puts(sf, "#   <op>[,<mode>] rx-add-byte          add a spurious byte to the received CEC message\n");
 	seq_puts(sf, "#   <op>[,<mode>] rx-remove-byte       remove the last byte from the received CEC message\n");
-	seq_puts(sf, "#   <op>[,<mode>] rx-arb-lost <poll>   generate a POLL message to trigger an arbitration lost\n");
+	seq_puts(sf, "#    any[,<mode>] rx-arb-lost [<poll>] generate a POLL message to trigger an arbitration lost\n");
 	seq_puts(sf, "#\n");
 	seq_puts(sf, "# TX error injection settings:\n");
 	seq_puts(sf, "#   tx-ignore-nack-until-eom           ignore early NACKs until EOM\n");