net: bgmac: fix reversed checks for clock control flag

This fixes regression introduced by patch adding feature flags. It was
already reported and patch followed (it got accepted) but it appears it
was incorrect. Instead of fixing reversed condition it broke a good one.

This patch was verified to actually fix SoC hanges caused by bgmac on
BCM47186B0.

Fixes: db791eb2 ("net: ethernet: bgmac: convert to feature flags")
Fixes: 4af1474e ("net: bgmac: Fix errant feature flag check")
Cc: Jon Mason <jon.mason@broadcom.com>
Signed-off-by: Rafał Miłecki <rafal@milecki.pl>
Signed-off-by: David S. Miller <davem@davemloft.net>