ARM: ux500: fix prcmu_is_cpu_in_wfi() calculation

ARM: ux500: fix prcmu_is_cpu_in_wfi() calculation

This function clearly never worked and always returns true,
as pointed out by gcc-7:

arch/arm/mach-ux500/pm.c: In function 'prcmu_is_cpu_in_wfi':
arch/arm/mach-ux500/pm.c:137:212: error: ?:
using integer constants in boolean context, the expression
will always evaluate to 'true' [-Werror=int-in-bool-context]

With the added braces, the condition actually makes sense.

Fixes: 34fe6f107eab ("mfd : Check if the other db8500 core is in WFI")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>