arm: mxs: Clear CPSR V bit to activate low vectors

arm: mxs: Clear CPSR V bit to activate low vectors

The MXS starts with CPSR V bit set, which makes the CPU jump to high vectors
in case of an exception. Those high vectors are located at 0xffff0000, which
is where the BootROM exception table is located as well. U-Boot should handle
exceptions on its own using its own exception handling code, which is located
at 0x0, i.e. at low vectors. Clear the CPSR V bit, so that the CPU would jump
to low vectors on exception instead, and therefore run the U-Boot exception
handling code.

Signed-off-by: Marek Vasut <marex@denx.de>
Reviewed-by: Fabio Estevam <festevam@gmail.com>