ARM: OMAP5: Fix build for PM code

It's CONFIG_SOC_OMAP5, not CONFIG_ARCH_OMAP5. Looks like make randconfig
builds have not hit this one yet.

Fixes: b3bf289c ("ARM: OMAP2+: Fix build with CONFIG_SMP and CONFIG_PM
is not set")
Acked-by: Santosh Shilimkar <ssantosh@kernel.org>
Signed-off-by: Tony Lindgren <tony@atomide.com>