sh: tmu: Changed switch statement to shift operation

Calculation of the bit position using switch statement can substitute
shift operation using ffs.
And removed unsed macro and variable.

Signed-off-by: Nobuhiro Iwamatsu <nobuhiro.iwamatsu.yj@renesas.com>
Signed-off-by: Nobuhiro Iwamatsu <iwamatsu@nigauri.org>