bnxt_en: Do not call sleeping hwmon_notify_event() from NAPI

Defer hwmon_notify_event() to bnxt_sp_task() workqueue because
hwmon_notify_event() can try to acquire a mutex shown in the stack trace
below.  Modify bnxt_event_error_report() to return true if we need to
schedule bnxt_sp_task() to notify hwmon.

  __schedule+0x68/0x520
  hwmon_notify_event+0xe8/0x114
  schedule+0x60/0xe0
  schedule_preempt_disabled+0x28/0x40
  __mutex_lock.constprop.0+0x534/0x550
  __mutex_lock_slowpath+0x18/0x20
  mutex_lock+0x5c/0x70
  kobject_uevent_env+0x2f4/0x3d0
  kobject_uevent+0x10/0x20
  hwmon_notify_event+0x94/0x114
  bnxt_hwmon_notify_event+0x40/0x70 [bnxt_en]
  bnxt_event_error_report+0x260/0x290 [bnxt_en]
  bnxt_async_event_process.isra.0+0x250/0x850 [bnxt_en]
  bnxt_hwrm_handler.isra.0+0xc8/0x120 [bnxt_en]
  bnxt_poll_p5+0x150/0x350 [bnxt_en]
  __napi_poll+0x3c/0x210
  net_rx_action+0x308/0x3b0
  __do_softirq+0x120/0x3e0

Cc: Guenter Roeck <linux@roeck-us.net>
Fixes: a19b4801 ("bnxt_en: Event handler for Thermal event")
Signed-off-by: Kalesh AP <kalesh-anakkur.purayil@broadcom.com>
Signed-off-by: Michael Chan <michael.chan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>