clocksource/arm_arch_timer: Fix arch_timer_mem_find_best_frame()

clocksource/arm_arch_timer: Fix arch_timer_mem_find_best_frame()

BugLink: https://bugs.launchpad.net/bugs/1713821
arch_timer_mem_find_best_frame() looks through ARCH_TIMER_MEM_MAX_FRAMES
frames even after finding matches to ensure the best frame is chosen,
which means the variable frame will point to the last valid frame but
not necessarily the best frame.

On Juno, we get the following error as the wrong frame is returned as the
best frame from arch_timer_mem_find_best_frame():

  arch_timer: Unable to map frame @ 0x0000000000000000
  arch_timer: Frame missing phys irq.
  Failed to initialize '/timer@2a810000': -22

Fix the issue by correctly returning the best frame from
arch_timer_mem_find_best_frame().

Fixes: c389d701dfb7 ("clocksource: arm_arch_timer: split MMIO timer probing.")
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Cc: Marc Zyngier <marc.zyngier@arm.com>
Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
Cc: linux-arm-kernel@lists.infradead.org
Link: http://lkml.kernel.org/r/1494246747-17267-1-git-send-email-sudeep.holla@arm.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
(cherry picked from commit f63d947c1673930bfc5f2f9bd1073a02c179a890)
Signed-off-by: dann frazier <dann.frazier@canonical.com>
Acked-by: Stefan Bader <stefan.bader@canonical.com>
Acked-by: Colin King <colin.king@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>