clk: mmp: add timer clock for pxa168/mmp2/pxa910

Timer has external fast clock, and it is a mux clock.
Add the timer clock type for timer driver.

Signed-off-by: Chao Xie <chao.xie@marvell.com>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
6 files changed