ARM: i.MX: Disable supervisor protect for i.MX51

ARM: i.MX: Disable supervisor protect for i.MX51

Most peripherals on the i.MX51 have an Off-Platform Peripheral Access
Control Register (OPACR) in which the access rights (together with the
MPROT registers) can be declared.
However, this does not seem to work for example for SSI1+SDMA, because the
supervisor bit is not set for the SDMA unit.
A similar problem was described in the patch for i.MX53 CPU
(ARM: i.MX53: globally disable supervisor protect), and the same solution
is applicable for i.MX51 CPU.
Patch has tested on custom board based on Digi CCMX-51 module (i.MX51).

Signed-off-by: Alexander Shiyan <shc_work@mail.ru>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>