OMAP: clock: fix compile warning

if building kernels without OMAP2 support, we
will see a warning such as:

arch/arm/mach-omap2/io.c: In function 'omap2_init_common_infrastructure':
arch/arm/mach-omap2/io.c:389:3: warning: statement with no effect
arch/arm/mach-omap2/io.c:391:3: warning: statement with no effect

Signed-off-by: Felipe Balbi <balbi@ti.com>
Signed-off-by: Paul Walmsley <paul@pwsan.com>