[PATCH] samples: fix the compile error about SAMPLE_VFIO_MDEV_ series

[<ye.xingchen@zte.com.cn>]

From: ye xingchen <ye.xingchen@zte.com.cn>

When CONFIG_VFIO = m, SAMPLE_VFIO_MDEV_MTTY, SAMPLE_VFIO_MDEV_MTTY and
SAMPLE_VFIO_MDEV_MBOCHS can be selected as:
CONFIG_SAMPLE_VFIO_MDEV_MTTY = y;
CONFIG_SAMPLE_VFIO_MDEV_MTTY = y;
CONFIG_SAMPLE_VFIO_MDEV_MBOCHS = y;

That will cause compile error such as:

ld: samples/vfio-mdev/mdpy.o: in function 'mdpy_remove':
samples/vfio-mdev/mdpy.c:294: undefined reference to
'vfio_unregister_group_dev'

ld: samples/vfio-mdev/mtty.o: in function 'mtty_remove':
samples/vfio-mdev/mtty.c:793: undefined reference to
'vfio_unregister_group_dev'

ld: samples/vfio-mdev/mbochs.o: in function 'mbochs_remove':
samples/vfio-mdev/mbochs.c:603: undefined reference to
'vfio_unregister_group_dev'

Add dependency make SAMPLE_VFIO_MDEV_MTTY, SAMPLE_VFIO_MDEV_MTTY and
SAMPLE_VFIO_MDEV_MBOCHS not allowed to set as y when
CONFIG_VFIO = m.

Signed-off-by: ye xingchen <ye.xingchen@zte.com.cn>
---
 samples/Kconfig | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/samples/Kconfig b/samples/Kconfig
index 56b191d128d8..44a09dfa8a0b 100644
--- a/samples/Kconfig
+++ b/samples/Kconfig
@@ -185,6 +185,7 @@ config SAMPLE_UHID

 config SAMPLE_VFIO_MDEV_MTTY
 	tristate "Build VFIO mtty example mediated device sample code"
+	depends on VFIO
 	select VFIO_MDEV
 	help
 	  Build a virtual tty sample driver for use as a VFIO
@@ -192,6 +193,7 @@ config SAMPLE_VFIO_MDEV_MTTY

 config SAMPLE_VFIO_MDEV_MDPY
 	tristate "Build VFIO mdpy example mediated device sample code"
+	depends on VFIO
 	select VFIO_MDEV
 	help
 	  Build a virtual display sample driver for use as a VFIO
@@ -209,6 +211,7 @@ config SAMPLE_VFIO_MDEV_MDPY_FB

 config SAMPLE_VFIO_MDEV_MBOCHS
 	tristate "Build VFIO mdpy example mediated device sample code"
+	depends on VFIO
 	select VFIO_MDEV
 	select DMA_SHARED_BUFFER
 	help
-- 
2.25.1