ARM i.MX6q: Add virtual 1/3.5 dividers in the LDB clock path

The ldb_di[01]_podf is implemented as a clk-divider that
divides by 1 or 2. In reality, the ldb_di[01]_ipu_div
dividers divide by either 3.5 or 7. Adding a fixed factor
of 1/3.5 fixes their children's clock rates.

This should probably be converted to rate table based dividers,
once available.

Cc: <stable@vger.kernel.org>
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
Signed-off-by: Steffen Trumtrar <s.trumtrar@pengutronix.de>
Signed-off-by: Shawn Guo <shawn.guo@linaro.org>