ARM: at91: move at91_pmc.h to include/linux/clk/at91_pmc.h

This patch moves at91_pmc.h header from machine specific directory
(arch/arm/mach-at91/include/mach/at91_pmc.h) to clk include directory
(include/linux/clk/at91_pmc.h).
We need this to avoid reference to machine specific headers in clk
drivers.

Signed-off-by: Boris BREZILLON <b.brezillon@overkiz.com>
Acked-by: Felipe Balbi <balbi@ti.com>
Acked-by: Mike Turquette <mturquette@linaro.org>
Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>