clk: hisilicon: fix warning from smatch

drivers/clk/hisilicon/clk-hi3620.c:338
mmc_clk_delay() warn: always true condition '(para >= 0) => (0-u32max >= 0)'

Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Zhangfei Gao <zhangfei.gao@linaro.org>
Signed-off-by: Mike Turquette <mturquette@linaro.org>