ARM: SAMSUNG: call clk_get_rate for debugfs rate files

c->rate is rarely set, call clk_get_rate on the clock to print
the value in /d/clock/.../rate.

Signed-off-by: Colin Cross <ccross@android.com>
Signed-off-by: Jonghwan Choi <jhbird.choi@samsung.com>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>