clk: samsung: Remove unused mout_user_aclk400_mcuisp_p4x12 variable

Remove unused 'mout_user_aclk400_mcuisp_p4x12' variable to fix GCC warning:

    drivers/clk/samsung/clk-exynos4412-isp.c:40:27: warning:
        'mout_user_aclk400_mcuisp_p4x12' defined but not used [-Wunused-const-variable=]

Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>