ARM: S3C64XX: Use chip_data to store the shift for EINTs

This makes all the functions that use the shift slightly smaller, one
instruction in most cases but more for ack() and maskack().

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Cc: Ben Dooks <ben-linux@fluff.org>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>