msm: clock-local: Fold unused reset-only amp_clk into amp_p_clk

The amp_p_clk is the only clock that goes to the DSI AHB bus
arbiter. The amp_clk existed in software for reset purposes only.
Combine these together so one clock can be used by software to
do all this.

Change-Id: I0e5f7a1489245d979b5460497d0a14d62ddcb68e
Signed-off-by: Matt Wagantall <mattw@codeaurora.org>