msm: clock-generic: Add half-integer divider support to mux-div clk

Add half-integer divider support. All the min/max_div have
been doubled if it supports half-integer divider. It means we can
divide by 2, 2.5, 3, 3.5, etc.

Change-Id: Id6a39e75387cf2ce601ed9889420b8da5ee85dfa
Signed-off-by: Xiaogang Cui <xiaogang@codeaurora.org>