ARM: mvebu: remove the workaround imprecise abort fault handler

This is not needed anymore. Handling a potentially pending imprecise
external abort left behind by the bootloader is now done in a slightly
safer way inside the common ARM startup code.

[gregory.clement@free-electrons.com: Beside the Armada 375 Z1 which
initially required this, is no more supported]

Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
Reviewed-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Gregory CLEMENT <gregory.clement@free-electrons.com>