ARM: mach-shmobile: rename clk_init() to shmobile_clk_init()

Rename clk_init() to shmobile_clk_init() to avoid a potential
future name space collision with the common clock framework.

Signed-off-by: Magnus Damm <damm@opensource.se>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>