scsi: docs: convert cxgb3i.txt to ReST

Link: https://lore.kernel.org/r/0708b62b6ec4f0dddc581e412bb02ba6476f4523.1583136624.git.mchehab+huawei@kernel.org
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>