clocksource: arm_arch_timer: clean up printk usage

clocksource: arm_arch_timer: clean up printk usage

Almost all string in the arm_arch_timer driver duplicate an common
prefix (though a few do not). For consistency, it would be better to use
pr_fmt(), and always use this prefix. At the same time, we may as well
clean up some whitespace issues in arch_timer_banner and
arch_timer_init.

No functional change.

Signed-off-by: Fu Wei <[email protected]>
Acked-by: Mark Rutland <[email protected]>
Tested-by: Xiongfeng Wang <[email protected]>
[Mark: reword commit message]
Signed-off-by: Mark Rutland <[email protected]>