ACPI / event: remove unneeded NULL pointer check

nla_data() cannot return NULL as it simply adds NLA_HDRLEN to the
passed pointer. The NULL pointer check is therefore superfluous.
Remove it.

Found by smatch:
  drivers/acpi/event.c:130 acpi_bus_generate_netlink_event() warn: can
  'event' even be NULL?

Signed-off-by: Mathias Krause <minipli@googlemail.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Merge branch 'acpi-assorted-next' into linux-next

* acpi-assorted-next:
  ACPI / event: remove unneeded NULL pointer check
Merge branch 'pm-cpufreq-next' into linux-next

* pm-cpufreq-next:
  intel_pstate: skip the driver if ACPI has power mgmt option
  cpufreq: ondemand: Remove redundant return statement
Merge branch 'powercap-next' into linux-next

* powercap-next:
  PowerCap: Fix build error with option -Werror=format-security
Merge branch 'acpi-video-next' into linux-next

* acpi-video-next:
  Revert "ACPI / video: Ignore BIOS initial backlight value for HP 250 G1"
  ACPI / video: Quirk initial backlight level 0
  ACPI / video: Fix initial level validity test
  ACPI / blacklist: fix name of ThinkPad Edge E530
Merge branch 'pm-runtime-next' into linux-next

* pm-runtime-next:
  PM / runtime: Use pm_runtime_put_sync() in __device_release_driver()
Merge branch 'pm-sleep-next' into linux-next

* pm-sleep-next:
  PM / hibernate: Avoid overflow in hibernate_preallocate_memory()