fpga: dfl: fix the definitions of type & feature_id for dfl devices

fpga: dfl: fix the definitions of type & feature_id for dfl devices

The value of the field dfl_device.type comes from the 12 bits register
field DFH_ID according to DFL spec. So this patch changes the definition
of the type field to u16.

Also it is not necessary to illustrate the valid bits of the type field
in comments. Instead we should explicitly define the possible values in
the enumeration type for it, because they are shared by hardware spec.
We should not let the compiler decide these values.

Similar changes are also applied to dfl_device.feature_id.

This patch also fixed the MODALIAS format according to the changes
above.

Reviewed-by: Tom Rix <trix@redhat.com>
Signed-off-by: Xu Yilun <yilun.xu@intel.com>
Signed-off-by: Moritz Fischer <mdf@kernel.org>
Link: https://lore.kernel.org/r/20210107043714.991646-4-mdf@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>