Fix typos in doc and comments

Changes persistant -> persistent. www.dictionary.com does not know
persistant (with an A), but should it be one of those things you can
spell in more than one correct way, let me know.

Signed-off-by: Jan Engelhardt <jengelh@gmx.de>
Signed-off-by: Adrian Bunk <bunk@stusta.de>
diff --git a/drivers/pci/Kconfig b/drivers/pci/Kconfig
index d0ba112..3cfb0a3 100644
--- a/drivers/pci/Kconfig
+++ b/drivers/pci/Kconfig
@@ -34,7 +34,7 @@
 
 	  It is very unwise to use this option if you are not using a
 	  boot process that can handle devices being created in any
-	  order.  A program that can create persistant block and network
+	  order.  A program that can create persistent block and network
 	  device names (like udev) is a good idea if you wish to use
 	  this option.