ARM: 5787/1: U300 COH 901 331 fixes

This will fix some small issues with the COH 901 331 RTC driver:
- Interrupt is disabled after alarm so that we don't fire
  multiple interrupts.
- We return 0 from the coh901331_alarm_irq_enable() ridding
  a compile warning.
- We alter the name in the U300 device registry to match that
  of the driver so they sucessfully resolve.

Signed-off-by: Linus Walleij <linus.walleij@stericsson.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>