ARM: OMAP: Fix compiler warning

Fix the following compiler warning (only visible with
CONFIG_OMAP_RESET_CLOCKS):

arch/arm/mach-omap1/clock.c: In function 'omap1_clk_disable_unused':
arch/arm/mach-omap1/clock.c:634: warning: 'return' with a value, in
function returning void

Signed-off-by: Andrzej Zaborowski <balrog@zabor.org>
Signed-off-by: Tony Lindgren <tony@atomide.com>