MLK-10103-1 ARM: imx: add VPU 352M for i.mx6q

When VPU freq is set to 352MHz, it needs to source clk
from PLL2_PFD2_396M, and PLL2_PFD2_396M need to change
freq to 352M, cpufreq's 396M setpoint will be removed.

Busfreq will be disabled as it needs PLL2_PFD2 to be
as 396MHz to achieve low power audio freq setpoint.

To enable VPU 352MHz feature, select it in menuconfig,
it is disabled by default.

Signed-off-by: Anson Huang <b20788@freescale.com>