ARM: S3C24XX: Add .get_rate callback for "camif-upll" clock

Add missing get_rate callback for the "camif-upll" clock, so frequency
of this clock is properly reported with clk_get_rate().

Signed-off-by: Sylwester Nawrocki <sylvester.nawrocki@gmail.com>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>