net: dsa: bcm_sf2: Clear IDDQ_GLOBAL_PWR bit for PHY

The PHY on BCM7278 has an additional bit that needs to be cleared:
IDDQ_GLOBAL_PWR, without doing this, the PHY remains stuck in reset out
of suspend/resume cycles.

Fixes: 0fe99338 ("net: dsa: bcm_sf2: Add support for BCM7278 integrated switch")
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>