net: bcmgenet: add missing braces to some if statements

checkpatch.pl flagged two locations that did not comply to "CHECK:
braces {} should be used on all arms of this statement", fix them.

Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>