[SCSI] Replace __FUNCTION__ with __func__ in iscsi_tcp.

__FUNCTION__ is gcc-specific, use __func__

(Update diff by Mike Christie)

Signed-off-by: Harvey Harrison <harvey.harrison@gmail.com>
Signed-off-by: Mike Christie <michaelc@cs.wisc.edu>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>