fsl/fman: Remove comment referring to non-existent function

fm_set_max_frm() existed in the Freescale SDK as a callback for an
early_param. When this code was ported to the upstream kernel the
early_param was converted to a module_param making the reference to the
function incorrect. The rest of the comment already does a good job of
explaining the parameter so removing the reference to the non-existent
function seems like the best thing to do.
Signed-off-by: NChris Packham <chris.packham@alliedtelesis.co.nz>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/ethernet/freescale/fman/fman.c

@@ -2439,9 +2439,6 @@ MODULE_PARM_DESC(fsl_fm_rx_extra_headroom, "Extra headroom for Rx buffers");
  * buffers when not using jumbo frames.
  * Must be large enough to accommodate the network MTU, but small enough
  * to avoid wasting skb memory.
- *
- * Could be overridden once, at boot-time, via the
- * fm_set_max_frm() callback.
  */
 static int fsl_fm_max_frm = FSL_FM_MAX_FRAME_SIZE;
 module_param(fsl_fm_max_frm, int, 0);