IB/mthca: remove redundant inner check of mdev->mthca_flags

The inner check for mdev->mthca_flags & MTHCA_FLAG_MSI_X is redundant
as this is already true because of the previous identical check in
an outer if statement.  Remove it

Detected by cppcheck:
(warning) Identical inner 'if' condition is always true.

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>