amd-xgbe: Simplify powerdown/powerup paths

amd-xgbe: Simplify powerdown/powerup paths

The caller parameter in xgbe_powerdown() and xgbe_powerup() was intended
to differentiate between driver and ioctl contexts, but the only
remaining usage is from the driver suspend/resume path.

Simplify this by:
- Removing the unused XGMAC_DRIVER_CONTEXT and XGMAC_IOCTL_CONTEXT
  macros
- Dropping the now-unused caller parameter
- Reordering operations in xgbe_powerdown() to disable NAPI before
  stopping TX/RX, matching the order used in xgbe_stop()

This makes the powerdown/powerup paths easier to follow and keeps the
ordering consistent with the rest of the driver.

Signed-off-by: Raju Rangoju <Raju.Rangoju@amd.com>
Link: https://patch.msgid.link/20260308092851.1510214-2-Raju.Rangoju@amd.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>