rtc: allow validated RTC_PIE_ON for non-root

rtc: allow validated RTC_PIE_ON for non-root

drivers/char/rtc.c allowed RTC_PIE_ON ioctls for non-root users, as long as
the current interval (set via RTC_IRQP_SET) is <= max_user_freq.  Allow
RTC_PIE_ON under the same conditions when /dev/rtc* is handled by the rtc
subsystem.

Signed-off-by: Bryan Kadzban <[email protected]>
Acked-by: Alessandro Zummo <[email protected]>
Cc: David Brownell <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>