[PATCH] hpet: fix division by zero in HPET_INFO

Fix a division by zero that happened when the HPET_INFO ioctl was called
before a timer frequency had been set.

Signed-off-by: Clemens Ladisch <clemens@ladisch.de>
Cc: Bob Picco <bob.picco@hp.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>