clk: use private clk struct to access clock flags

clk: use private clk struct to access clock flags

There may be cases where the flags set for a clock is not available.
This is usually the case with clocks which have been retrieved using
clk_request(). However, clock flags are found in their respective
private clock struct, so use that instead.

Signed-off-by: Kaustabh Chakraborty <kauschluss@disroot.org>
Signed-off-by: Minkyu Kang <mk7.kang@samsung.com>