ARM: mach-ux500: enable 128KB way L2 cache on DB8540

DB8540 L2 was configured with 64KB way size, but it has 128KB as AP9540.

Fix this by modifying ux500_l2x0_init() to use 128KB way size for all
cpus in the x540 family.

Signed-off-by: Maxime Coquelin <maxime.coquelin@stericsson.com>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Fabio Baltieri <fabio.baltieri@linaro.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>