ARM: OMAP: clk_disable_unused: init section mismatch

Fix the following warning when OMAP_RESET_CLOCKS is enabled:

WARNING: vmlinux.o(.data+0x33a0): Section mismatch: reference to .init.text:omap2_clk_disable_unused (between 'omap2_clk_functions' and 'osc_ck')

omap2_clk_disable_unused cannot be declared __init as it part of a
struct where the rest of the functions are not __init.

Signed-off-by: Kevin Hilman <khilman@mvista.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>