cpuidle/pseries: Make symbol 'pseries_idle_driver' static

The sparse tool complains as follows:

drivers/cpuidle/cpuidle-pseries.c:25:23: warning:
 symbol 'pseries_idle_driver' was not declared. Should it be static?

'pseries_idle_driver' is not used outside of this file, so marks
it static.

Reported-by: Hulk Robot <[email protected]>
Signed-off-by: Wei Yongjun <[email protected]>
Signed-off-by: Michael Ellerman <[email protected]>
Link: https://lore.kernel.org/r/[email protected]

drivers/cpuidle/cpuidle-pseries.c

@@ -22,7 +22,7 @@
 #include <asm/idle.h>
 #include <asm/plpar_wrappers.h>
 
-struct cpuidle_driver pseries_idle_driver = {
+static struct cpuidle_driver pseries_idle_driver = {
 	.name             = "pseries_idle",
 	.owner            = THIS_MODULE,
 };