msm: clock: Move fixed_clk to clock-generic header

fixed_clk is a simple wrapper for struct clk. It should be in
clock-generic header instead of clock-local2.h

Change-Id: I24e42f91d84fe34cf29938f48979879ca7bf8f2c
Signed-off-by: Junjie Wu <junjiew@codeaurora.org>