clk: imx: gate2: Remove unused variable ret

This patch fixes below warning reported by coccicheck:

./clk-gate2.c:57:5-8: Unneeded variable: "ret". Return "0" on line 68

Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Zou Wei <zou_wei@huawei.com>
Reviewed-by: Stephen Boyd <sboyd@kernel.org>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>