media: cedrus: Add helper for checking capabilities

There is several different Cedrus cores with varying capabilities, so
some operations like listing formats depends on checks if feature is
supported or not.

Currently check for capabilities is only in format handling functions,
but it will be used also elsewhere later. Let's convert this check to
helper and while at it, also simplify it. There is no need to check if
capability mask is zero, condition will still work properly.

No functional changes intended.

Signed-off-by: Jernej Skrabec <jernej.skrabec@gmail.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>