cxgb4: Address various sparse warnings

This patch fixes type assignment issues, function definition and symbol
shadowing which triggered sparse warnings.

Signed-off-by: Jay Hernandez <jay@chelsio.com>
Signed-off-by: Vipul Pandya <vipul@chelsio.com>
Signed-off-by: David S. Miller <davem@davemloft.net>