fs: cramfs: add MODULE_DESCRIPTION()

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

Signed-off-by: Jeff Johnson <quic_jjohnson@quicinc.com>
Link: https://lore.kernel.org/r/20240527-md-fs-cramfs-v1-1-fa697441c8c5@quicinc.com


Reviewed-by: Nicolas Pitre <nico@fluxnic.net>
Acked-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Christian Brauner <brauner@kernel.org>