Fix this sparse warnings:
  drivers/ide/ide-disk_proc.c:130:11: warning: Using plain integer as NULL pointer
  drivers/ide/ide-floppy_proc.c:32:11: warning: Using plain integer as NULL pointer
  drivers/ide/ide-proc.c:234:11: warning: Using plain integer as NULL pointer
  drivers/ide/ide-tape.c:2141:11: warning: Using plain integer as NULL pointer
Signed-off-by: NHannes Eder <hannes@hanneseder.net>
Cc: trivial@kernel.org
Cc: kernel-janitors@vger.kernel.org
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: NBartlomiej Zolnierkiewicz <bzolnier@gmail.com>

While at it:
- IDEDISK_VERSION -> IDE_GD_VERSION
- ide_cacheflush_p() -> ide_disk_flush()
- init_idedisk_capacity() -> ide_disk_init_capacity()
- idedisk_set_doorlock() -> ide_disk_set_doorlock()
- idedisk_setup() -> ide_disk_setup()

- ide_disk_capacity() -> ide_gd_capacity()
- ide_disk_remove() -> ide_gd_remove()
- ide_disk_probe() -> ide_gd_probe()
- ide_disk_resume() -> ide_gd_resume()
- ide_device_shutdown() -> ide_gd_shutdown()
- idedisk_driver -> ide_gd_driver
- idedisk_open() -> ide_gd_open()
- idedisk_release() -> ide_gd_release()
- idedisk_getgeo() -> ide_gd_getgeo()
- idedisk_media_changed() -> ide_gd_media_changed()
- idedisk_revalidate_disk() -> ide_gd_revalidate_disk()
- idedisk_ops -> ide_gd_ops
- idedisk_init() -> ide_gd_init()
- idedisk_exit() -> ide_gd_exit()

There should be no functional changes caused by this patch.
Acked-by: NBorislav Petkov <petkovbb@gmail.com>
Signed-off-by: NBartlomiej Zolnierkiewicz <bzolnier@gmail.com>

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: NBartlomiej Zolnierkiewicz <bzolnier@gmail.com>