drm/tidss: Drop pointless static qualifier in dispc_find_csc()

There is no need to have the 'const struct dispc_csc_coef *coef'
variable static since new value always be assigned before use it.

Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Reviewed-by: Jyri Sarha <jsarha@ti.com>
Tested-by: Jyri Sarha <jsarha@ti.com>
Signed-off-by: Jyri Sarha <jsarha@ti.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200227065057.92766-1-yuehaibing@huawei.com