net: ravb: Fix missing rtnl lock in suspend/resume path

net: ravb: Fix missing rtnl lock in suspend/resume path

Fix the suspend/resume path by ensuring the rtnl lock is held where
required. Calls to ravb_open, ravb_close and wol operations must be
performed under the rtnl lock to prevent conflicts with ongoing ndo
operations.

Without this fix, the following warning is triggered:
[   39.032969] =============================
[   39.032983] WARNING: suspicious RCU usage
[   39.033019] -----------------------------
[   39.033033] drivers/net/phy/phy_device.c:2004 suspicious
rcu_dereference_protected() usage!
...
[   39.033597] stack backtrace:
[   39.033613] CPU: 0 UID: 0 PID: 174 Comm: python3 Not tainted
6.13.0-rc7-next-20250116-arm64-renesas-00002-g35245dfdc62c #7
[   39.033623] Hardware name: Renesas SMARC EVK version 2 based on
r9a08g045s33 (DT)
[   39.033628] Call trace:
[   39.033633]  show_stack+0x14/0x1c (C)
[   39.033652]  dump_stack_lvl+0xb4/0xc4
[   39.033664]  dump_stack+0x14/0x1c
[   39.033671]  lockdep_rcu_suspicious+0x16c/0x22c
[   39.033682]  phy_detach+0x160/0x190
[   39.033694]  phy_disconnect+0x40/0x54
[   39.033703]  ravb_close+0x6c/0x1cc
[   39.033714]  ravb_suspend+0x48/0x120
[   39.033721]  dpm_run_callback+0x4c/0x14c
[   39.033731]  device_suspend+0x11c/0x4dc
[   39.033740]  dpm_suspend+0xdc/0x214
[   39.033748]  dpm_suspend_start+0x48/0x60
[   39.033758]  suspend_devices_and_enter+0x124/0x574
[   39.033769]  pm_suspend+0x1ac/0x274
[   39.033778]  state_store+0x88/0x124
[   39.033788]  kobj_attr_store+0x14/0x24
[   39.033798]  sysfs_kf_write+0x48/0x6c
[   39.033808]  kernfs_fop_write_iter+0x118/0x1a8
[   39.033817]  vfs_write+0x27c/0x378
[   39.033825]  ksys_write+0x64/0xf4
[   39.033833]  __arm64_sys_write+0x18/0x20
[   39.033841]  invoke_syscall+0x44/0x104
[   39.033852]  el0_svc_common.constprop.0+0xb4/0xd4
[   39.033862]  do_el0_svc+0x18/0x20
[   39.033870]  el0_svc+0x3c/0xf0
[   39.033880]  el0t_64_sync_handler+0xc0/0xc4
[   39.033888]  el0t_64_sync+0x154/0x158
[   39.041274] ravb 11c30000.ethernet eth0: Link is Down

Reported-by: Claudiu Beznea <claudiu.beznea.uj@bp.renesas.com>
Closes: https://lore.kernel.org/netdev/4c6419d8-c06b-495c-b987-d66c2e1ff848@tuxon.dev/
Fixes: 0184165b2f42 ("ravb: add sleep PM suspend/resume support")
Signed-off-by: Kory Maincent <kory.maincent@bootlin.com>
Tested-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>