spi: rockchip-sfc: Fix assigned but never used return error codes

spi: rockchip-sfc: Fix assigned but never used return error codes

Currently there are two places where the error return variable ret is
being assigned -ETIMEDOUT on timeout errors and this value is not
being returned. Fix this by returning -ETIMEDOUT rather than redundantly
assiging it to ret.

Addresses-Coverity: ("Unused value")
Fixes: 0b89fc0a367e ("spi: rockchip-sfc: add rockchip serial flash controller")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Link: https://lore.kernel.org/r/20210818141051.36320-1-colin.king@canonical.com
Signed-off-by: Mark Brown <broonie@kernel.org>