timer/exynos4210_mct: Remove redundant statement in exynos4210_mct_write()

timer/exynos4210_mct: Remove redundant statement in exynos4210_mct_write()

Clang static code analyzer show warning:
hw/timer/exynos4210_mct.c:1370:9: warning: Value stored to 'index' is never read
        index = GET_L_TIMER_CNT_REG_IDX(offset, lt_i);
        ^       ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
hw/timer/exynos4210_mct.c:1399:9: warning: Value stored to 'index' is never read
        index = GET_L_TIMER_CNT_REG_IDX(offset, lt_i);
        ^       ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
hw/timer/exynos4210_mct.c:1441:9: warning: Value stored to 'index' is never read
        index = GET_L_TIMER_CNT_REG_IDX(offset, lt_i);
        ^       ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Reported-by: Euler Robot <euler.robot@huawei.com>
Signed-off-by: Chen Qun <kuhn.chenqun@huawei.com>
Reviewed-by: Laurent Vivier <laurent@vivier.eu>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-Id: <20200325025919.21316-4-kuhn.chenqun@huawei.com>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>