Nokia RX-51: Do not call secure PPA routine on non secure devices

Since commit 41623c91 u-boot running in qemu is
crashing in function do_omap3_emu_romcode_call(). RX-51 board uses this function
for Cortex-A8 errata 430973 workaround (Set IBE bit in ACR) which is needed only
on real secure device and not in qemu.

This board patch just disable calling secure PPA routine on non secure devices.
Qemu implements GP device and with this patch u-boot is working in qemu again.

Signed-off-by: Pali Rohár <pali.rohar@gmail.com>
Acked-by: Pavel Machek <pavel@ucw.cz>