msm: camera: Discontinue use of clk_set_min_rate()

Support for the proprietary clk_set_min_rate() will soon be removed.
Move away from it. Call clk_set_rate() directly with an exact rate
where possible, and use clk_round_round() in conjunction with
clk_set_rate() when an exact rate is not known.

Change-Id: I030c93c976f516a3ec91844ce2e5d752f56cdb9a
Signed-off-by: Matt Wagantall <mattw@codeaurora.org>