cavium: Fix return values of the probe function

[ Upstream commit c69b2f46876825c726bd8a97c7fa852d8932bc32 ]

During the process of driver probing, the probe function should return < 0
for failure, otherwise, the kernel will treat value > 0 as success.

Signed-off-by: Zheyu Ma <zheyuma97@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>