msm: msm_bus: Don't enable/disable QoS clks during IO throttling modes

When modifying the QoS modes for a bus master port there is no need to
enable/disable the bus clocks needed to program the QoS registers since
the IO throttling is done after the bus clocks are already enabled.

Change-Id: I4e278f51bfcba52d5ee000181901110495ca0b2a
Signed-off-by: Girish Mahadevan <girishm@codeaurora.org>