scsi: libfc: Add some kernel-doc comments

scsi: libfc: Add some kernel-doc comments

Complete the kernel-doc notation for enum fc_lport_state. This fixes 7
kernel-doc warnings.

 - In struct fc_rport_priv, change 'event_callback' to 'lld_event_callback'
   to match the struct member name.

 - In struct fc_fcp_pkt, add a description for 'timer_delay' to eliminate
   one kernel-doc warning.

 - Add return value notation for 3 functions. This fixes 3 kernel-doc
   warnings.

There are still 12 warnings for struct members not described in struct
fc_rport_priv and struct fc_lport, e.g:

libfc.h:218: warning: Function parameter or struct member 'event' not described in 'fc_rport_priv'
libfc.h:760: warning: Function parameter or struct member 'vlan' not described in 'fc_lport'

Warnings that are fixed in this patch:

libfc.h:75: warning: Enum value 'LPORT_ST_RNN_ID' not described in enum 'fc_lport_state'
libfc.h:75: warning: Enum value 'LPORT_ST_RSNN_NN' not described in enum 'fc_lport_state'
libfc.h:75: warning: Enum value 'LPORT_ST_RSPN_ID' not described in enum 'fc_lport_state'
libfc.h:75: warning: Enum value 'LPORT_ST_RPA' not described in enum 'fc_lport_state'
libfc.h:75: warning: Enum value 'LPORT_ST_DHBA' not described in enum 'fc_lport_state'
libfc.h:75: warning: Enum value 'LPORT_ST_DPRT' not described in enum 'fc_lport_state'
libfc.h:75: warning: Excess enum value 'LPORT_ST_RPN_ID' description in 'fc_lport_state'

libfc.h:218: warning: Excess struct member 'event_callback' description in 'fc_rport_priv'

libfc.h:793: warning: No description found for return value of 'fc_lport_test_ready'
libfc.h:835: warning: No description found for return value of 'fc_lport_init_stats'
libfc.h:856: warning: No description found for return value of 'lport_priv'

Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Link: https://lore.kernel.org/r/20240424050038.31403-1-rdunlap@infradead.org
Cc: Hannes Reinecke <hare@suse.de>
Cc: James E.J. Bottomley <James.Bottomley@HansenPartnership.com>
Cc: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>