arm: Move excnames[] array into arm_log_exceptions()

The excnames[] array is defined in internals.h because we used
to use it from two different source files for handling logging
of AArch32 and AArch64 exception entry. Refactoring means that
it's now used only in arm_log_exception() in helper.c, so move
the array into that function.

Suggested-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Message-id: 1491821097-5647-1-git-send-email-peter.maydell@linaro.org