net: stmmac: remove stmmac_hw_setup() excess documentation parameter

The kernel build bot reports:

Warning: drivers/net/ethernet/stmicro/stmmac/stmmac_main.c:3438 Excess function parameter 'ptp_register' description in 'stmmac_hw_setup'

Fix it.

Reported-by: kernel test robot <lkp@intel.com>
Fixes: 98d8ea5 ("net: stmmac: move timestamping/ptp init to stmmac_hw_setup() caller")
Closes: https://lore.kernel.org/oe-kbuild-all/202509290927.svDd6xuw-lkp@intel.com/
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Link: https://patch.msgid.link/E1v38Y7-00000008UCQ-3w27@rmk-PC.armlinux.org.uk
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: Russell King (Oracle)

drivers/net/ethernet/stmicro/stmmac/stmmac_main.c

@@ -3400,7 +3400,6 @@ static void stmmac_safety_feat_configuration(struct stmmac_priv *priv)
 /**
  * stmmac_hw_setup - setup mac in a usable state.
  *  @dev : pointer to the device structure.
- *  @ptp_register: register PTP if set
  *  Description:
  *  this is the main function to setup the HW in a usable state because the
  *  dma engine is reset, the core registers are configured (e.g. AXI,