Some rtc-twl4030 cleanup, which among other things adds up to
using about 10% less object code:

 - Remove:
    * broken/unfixable "periodic" IRQ support (2^N Hz)
    * duplicated constants in the header file
    * pointless stuff:
       + support for settable epoch
       + memset() calls
       + indirection when reading time and alarm
       + indirection when enabling irqs
    * needless ifdeffery for reading irq enable register
 - IRQ updates:
    * group irq enable/disable utilities together
    * cache irq enable register
    * now disable any old alarm irq before setting alarm
 - Comment updates
    * fix up my copyright attribution (old omap1 code)
    * more correctly describe the rtc mask/set ops
    * have a single place describe the register vs tm_* differences
 - Other:
    * don't support "current" dates in the 20th century
    * switch over to bcd2bin()/bin2bcd()
    * prefer dev_err() and better messages to printk(KERN_ERR...)
    * correct some KERN_WARNING messages (should have been pr_err)
    * whitespace bugs
    * misc

The bugs fixed here are removing "periodic" IRQ support, and
some of the messaging.  Update IRQs still misbehave (two per
second, not one!), and the alarm isn't wake-enabled.
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Tony Lindgren <tony@atomide.com>