media: v4l2-subdev: get rid of __V4L2_SUBDEV_MK_GET_TRY() macro

media: v4l2-subdev: get rid of __V4L2_SUBDEV_MK_GET_TRY() macro

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media: v4l2-subdev: get rid of __V4L2_SUBDEV_MK_GET_TRY() macro

The __V4L2_SUBDEV_MK_GET_TRY() macro is used to define
3 functions that have the same arguments. The code of those
functions is simple enough to just declare them, de-obfuscating
the code.

While here, replace BUG_ON() by WARN_ON() as there's no reason
why to panic the Kernel if this fails.

Acked-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>