add a help text for BLK_DEV_GENERIC

This fixes kernel Bugzilla #4933.
Signed-off-by: NAdrian Bunk <bunk@stusta.de>

drivers/ide/Kconfig

@@ -383,6 +383,9 @@ config BLK_DEV_OFFBOARD
 config BLK_DEV_GENERIC
 	tristate "Generic PCI IDE Chipset Support"
 	depends on BLK_DEV_IDEPCI
+        help
+          This option provides generic support for various PCI IDE Chipsets
+          which otherwise might not be supported.
 
 config BLK_DEV_OPTI621
 	tristate "OPTi 82C621 chipset enhanced support (EXPERIMENTAL)"