spi: a3700: make a3700_spi_init() return void

Fix the following coccicheck warning:

drivers/spi/spi-armada-3700.c:283:8-11: Unneeded variable: "ret". Return
"0" on line 315

Signed-off-by: Jason Yan <yanaijie@huawei.com>
Link: https://lore.kernel.org/r/20200506061911.19923-1-yanaijie@huawei.com


Signed-off-by: Mark Brown <broonie@kernel.org>