arm: bL_switcher:k Use ktime_get_real_ns()

Use the nanoseconds based interface instead of converting from a
timespec.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: linux-arm-kernel@lists.infradead.org
Signed-off-by: John Stultz <john.stultz@linaro.org>