net: lan743x: fix building without CONFIG_PTP_1588_CLOCK

net: lan743x: fix building without CONFIG_PTP_1588_CLOCK

Building without CONFIG_PTP_1588_CLOCK results in multiple failures,
this was obviously not well tested:

drivers/net/ethernet/microchip/lan743x_ptp.c: In function 'lan743x_ptp_isr':
drivers/net/ethernet/microchip/lan743x_ptp.c:781:28: error: 'struct lan743x_ptp' has no member named 'ptp_clock'; did you mean 'tx_ts_lock'?
   ptp_schedule_worker(ptp->ptp_clock, 0);
                            ^~~~~~~~~
                            tx_ts_lock
drivers/net/ethernet/microchip/lan743x_ptp.c: In function 'lan743x_ptp_open':
drivers/net/ethernet/microchip/lan743x_ptp.c:879:6: error: unused variable 'ret' [-Werror=unused-variable]
  int ret = -ENODEV;
      ^~~
At top level:
drivers/net/ethernet/microchip/lan743x_ptp.c:63:13: error: 'lan743x_ptp_tx_ts_enqueue_ts' defined but not used [-Werror=unused-function]
 static void lan743x_ptp_tx_ts_enqueue_ts(struct lan743x_adapter *adapter,
             ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
cc1: all warnings being treated as errors
drivers/net/ethernet/microchip/lan743x_ethtool.c: In function 'lan743x_ethtool_get_ts_info':
drivers/net/ethernet/microchip/lan743x_ethtool.c:558:19: error: 'struct lan743x_ptp' has no member named 'ptp_clock'; did you mean 'tx_ts_lock'?

Those #ifdef checks are hard to get right, replace them all with
IS_ENABLED() checks that leave the same code visible to the compiler
but let it optimize out the unused bits based on the configuration.

Fixes: 07624df1c9ef ("lan743x: lan743x: Add PTP support")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: David S. Miller <davem@davemloft.net>