Put default ea handler implementation into function plat_default_ea_handler()
which just print verbose information and panic, so it can be called also
from overwritten / weak function plat_ea_handler() implementation.

Replace every custom implementation of printing verbose error message of
external aborts in custom plat_ea_handler() functions by a common
implementation from plat_default_ea_handler() function.
Signed-off-by: Pali Rohár <pali@kernel.org>
Change-Id: I15897f61b62b4c3c29351e693f51d4df381f3b98