clockchips.h: kernel-doc fix

Fix misnamed fields of 'struct clock_event_device' in the kernel-doc
comment.  Convert the acronyms to uppercase, while at it...

Signed-off-by: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>