cxgb4: Remove preprocessor check for CONFIG_CXGB4_DCB

In commit dc9daab2

 ("cxgb4: Added support in debugfs to dump
sge_qinfo") a preprocessor check for CONFIG_CXGB4_DCB got added, which should
have been CONFIG_CHELSIO_T4_DCB. After adding the right preprocessor, build
fails due to missing function ethqset2pinfo. Fixing that as well.

V2: Updated description since the patch also fixes build failure

Reported-by: Paul Bolle <pebolle@tiscal.nl>
Signed-off-by: Hariprasad Shenai <hariprasad@chelsio.com>
Signed-off-by: David S. Miller <davem@davemloft.net>