fs/adfs: add MODULE_DESCRIPTION

Fix the 'make W=1' issue:
WARNING: modpost: missing MODULE_DESCRIPTION() in fs/adfs/adfs.o

Signed-off-by: Jeff Johnson <quic_jjohnson@quicinc.com>
Link: https://lore.kernel.org/r/20240523-md-adfs-v1-1-364268e38370@quicinc.com


Signed-off-by: Christian Brauner <brauner@kernel.org>