Revert "ixl: Increase tx/rx ring size to 8160"

iflib enforces powerof2 on the ring size:
panic: Assertion powerof2(sctx->isc_nrxd_max[i])

Revert until this change is better understood.

Reported by: tuexen

This reverts commit 14561f1eda85fabfba2d764ca11e064ed871224e.