PM: Make CONFIG_PM depend on (CONFIG_PM_SLEEP || CONFIG_PM_RUNTIME)

From the users' point of view CONFIG_PM is really only used for
making it possible to set CONFIG_SUSPEND, CONFIG_HIBERNATION,
CONFIG_PM_RUNTIME and (surprisingly enough) CONFIG_XEN_SAVE_RESTORE
(CONFIG_PM_OPP also depends on CONFIG_PM, but quite artificially).
However, both CONFIG_SUSPEND and CONFIG_HIBERNATION require platform
support (independent of CONFIG_PM) and it is not quite obvious that
CONFIG_PM has to be set for CONFIG_XEN_SAVE_RESTORE to be available.
Thus, from the users' point of view, it would be more logical to
automatically select CONFIG_PM if any of the above options depending
on it are set.

Make CONFIG_PM depend on (CONFIG_PM_SLEEP || CONFIG_PM_RUNTIME),
which will cause it to be selected when any of CONFIG_SUSPEND,
CONFIG_HIBERNATION, CONFIG_PM_RUNTIME, CONFIG_XEN_SAVE_RESTORE is
set and will clarify its meaning.

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
diff --git a/arch/x86/xen/Kconfig b/arch/x86/xen/Kconfig
index 5b54892..2c876ed 100644
--- a/arch/x86/xen/Kconfig
+++ b/arch/x86/xen/Kconfig
@@ -38,7 +38,7 @@
 
 config XEN_SAVE_RESTORE
        bool
-       depends on XEN && PM
+       depends on XEN
        default y
 
 config XEN_DEBUG_FS