cxgb4: fix delete filter entry fail in unload path

Currently, the hardware TID index is assumed to start from index 0.
However, with the following changeset,

commit c2193999 ("cxgb4: add support for high priority filters")

hardware TID index can start after the high priority region, which
has introduced a regression resulting in remove filters entry
failure for cxgb4 unload path. This patch fix that.

Fixes: c2193999 ("cxgb4: add support for high priority filters")
Signed-off-by: Shahjada Abul Husain <shahjada@chelsio.com>
Signed-off-by: David S. Miller <davem@davemloft.net>