ide-disk: move /proc handling to ide-disk_proc.c (take 3)

While at it:
- idedisk_capacity() -> ide_disk_capacity()
- idedisk_proc[] -> ide_disk_proc[]
- idedisk_settings[] -> ide_disk_settings[]

v2/3:
Build fix for CONFIG_IDE_PROC_FS=n from Elias Oltmanns.

Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
diff --git a/drivers/ide/Makefile b/drivers/ide/Makefile
index 57b252b..e6e7811 100644
--- a/drivers/ide/Makefile
+++ b/drivers/ide/Makefile
@@ -41,6 +41,7 @@
 ide-floppy_mod-y += ide-floppy.o ide-floppy_ioctl.o
 
 ifeq ($(CONFIG_IDE_PROC_FS), y)
+	ide-disk_mod-y += ide-disk_proc.o
 	ide-floppy_mod-y += ide-floppy_proc.o
 endif