soc: bcm: raspberrypi-power: Fix use of __packed

Commit a09cd356 ("ARM: bcm2835: add rpi power domain driver")
attempted to annotate the structure rpi_power_domain_packet with
__packed but introduced a typo and made it named __packet instead. Just
drop the annotation since the structure is naturally aligned already.

Fixes: a09cd356

 ("ARM: bcm2835: add rpi power domain driver")
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>