clk: msm: clock: Do not allow setting rate on mmss_mmagic_ahb_clk

Remove support to allow setting a rate on the ahb_clk_src
using the mmss_mmagic_ahb_clk. The bus driver should be the
only one setting the AHB rate by using the ahb_clk_src
reference directly.

Change-Id: I4426af89c2ae567b246790b8a3218001456c15ec
Signed-off-by: Deepak Katragadda <dkatraga@codeaurora.org>