[SCSI] cxgb3i: fix select/depend problem

cxgb3i requires the cxgb3 net driver, so it selects it.  However,
cxgb3 has dependencies which the select cannot see.  Fix this by
separating out the cxgb3 dependencies into a separate hidden config
option (CONFIG_CHELSIO_T3_DEPENDS) and make both cxgb3 and cxgb3i
depend on it.

Reported-by: Randy Dunlap <randy.dunlap@oracle.com>
Cc: Karen Xie <kxie@chelsio.com>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>