ARM: shmobile: Take cpuidle dependencies into account correctly

The sh7372's cpuidle code uses cpu_suspend() and cpu_resume() in
its implementation of the .enter() callback for deeper C-states, so
make ARCH_SH7372 select ARM_CPU_SUSPEND if CPU_IDLE is set to satisfy
all of the build dependencies (it has to be selected for CONFIG_PM
as well for the system suspend handling).

[rjw: Added the subject and changelog.]
Signed-off-by: Magnus Damm <damm@opensource.se>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>

arch/arm/mach-shmobile/Kconfig

@@ -19,6 +19,7 @@ config ARCH_SH7372
 	select CPU_V7
 	select SH_CLK_CPG
 	select ARCH_WANT_OPTIONAL_GPIOLIB
+	select ARM_CPU_SUSPEND if PM || CPU_IDLE
 
 config ARCH_SH73A0
 	bool "SH-Mobile AG5 (R8A73A00)"