media: mxl5005s: drop some dead code

As reported by clang (with W=1), the ctrlVal var is never used.

Yet, there are even some loops to estimate it. As this is dead
code, remove it. If ever needed, someone could revert this
patch.

Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>