ARM: 9172/1: amba: Cleanup amba pclk operation

There is no user about amba_pclk_[un]prepare() besides pl330.c,
directly use clk_[un]prepare(). After this, all the function about
amba pclk operation, enable, disable, [un]prepare could be killed.

Acked-by: Vinod Koul <vkoul@kernel.org>
Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>