plat/arm: Make crash console functions strong

plat/arm: Make crash console functions strong

In Arm platforms the crash console doesn't print anything if the crash
happens early enough. This happens in all images, not only BL1. The
reason is that they the files ``plat/common/aarch64/platform_helpers.S``
and ``plat/arm/common/aarch64/arm_helpers.S``, and the crash console
functions are defined as weak in both files. In practice, the linker
can pick the one in ``plat/common``, which simply switches the multi
console to crash mode when it wants to initialize the crash console.
In the case of Arm platforms, there are no console drivers registered
at that point, so nothing is printed.

This patch makes the functions in plat/arm strong so that they override
the weak functions in plat/common.

Change-Id: Id358db7d2567d7df0951790a695636cf6c9ac57f
Signed-off-by: Antonio Nino Diaz <[email protected]>