[POWERPC] linkstation updates

1. Fix RTC type - it is a rs5c372a, not rs5c372b
2. Configure both UART interrupts edge-triggered
3. Add a license header to ls_uart.c
4. Check for running on linkstation in a late_initcall() function. Needed
   for multiplatform builds, even though linkstation doesn't support them
   yet
5. Remove unneeded #include from linkstation.c

Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>