samples: configfs: add missing MODULE_DESCRIPTION() macro

make allmodconfig && make W=1 C=1 reports:
WARNING: modpost: missing MODULE_DESCRIPTION() in samples/configfs/configfs_sample.o

Add the missing invocation of the MODULE_DESCRIPTION() macro.

Signed-off-by: Jeff Johnson <quic_jjohnson@quicinc.com>
Nacked-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20240601-md-samples-configfs-v1-1-83ef2d3c0088@quicinc.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>