drivers: sensor: lsm6dsl: Fix typos

In .h there are few typos that are fixed in this commit:

  - Delete LSM6DSL_REG_CTRL3_C and LSM6DSL_REG_CTRL9_XL
    register sections duplication.
  - Fix LSM6DSL_REG_CTRL6_C address.

Signed-off-by: Armando Visconti <armando.visconti@st.com>